Produced by Nick Hodson of London, England




The Gay Triangle
The Romance of the First Air Adventurers.
By William Le Queux
Published by Jarrolds, Lonodn.

The Gay Triangle, by William Le Queux.

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THE GAY TRIANGLE, BY WILLIAM LE QUEUX.

CHAPTER ONE.

THE MYSTERY OF RASPUTIN'S JEWELS.

From a derelict shed adjoining a lonely road which stretched for miles
across the Norfolk fens, a strange shape slid silently into the night
mist.  It was a motor-car of an unfamiliar design.  The body, of
gleaming aluminium, was of unusual width, and was lifted high above the
delicate chassis and spidery bicycle wheels that seemed almost too
fragile to bear the weight of an engine.

Noiselessly the strange car backed out of the shed.  There was no
familiar _teuf-teuf_ of the motor-engine; so silent was the car that it
might have been driven by electricity, save that the air was filled with
the reek of petrol.

Swinging round on the grass of the meadow, the car headed for the
gateway, turned into the road, and sped along silently for a few miles.

It halted at length at a point where the narrow roadway widened somewhat
and ran along an elevated embankment evidently constructed to raise the
road above flood-level.

As the car came to rest, two leather-helmeted figures descended from the
tiny cockpit in the body of it.  One was a slim young fellow of
twenty-five or twenty-six; the other, despite the clinging motor
costume, showed feminine grace in every movement.  It was a young girl,
evidently in the early twenties.

The two set busily to work, and in a few minutes their strange car had
undergone a wonderful transformation.

From each side shot out long twin telescopic rods.  These, swiftly
joined together by rapidly unrolled strips of fabric, soon resolved
themselves into the wings of a tiny monoplane.  From a cleverly hidden
trap-door in the front of the car, appeared an extending shaft bearing a
small propeller, whose twin blades, hinged so as to fold alongside the
shaft when not in use, were quickly spread out and locked into position.
A network of wire stays running from the wings to the fuselage of the
car were speedily hooked up and drawn taut.

Then the two mysterious figures climbed again into the transformed car.
There was a low, deep hum as the propellers began to revolve, the
monoplane shot forward a few yards along the road, then lifted
noiselessly, and, graceful and silent as a night-bird, vanished into the
shrouding mist.

The adventures of the Gay Triangle had begun!

------------------------------------------------------------------------

Dick Manton, lounging idly in the Assembly Hall of the little town of
Fenways, in the centre of the Norfolk Broads, watched with eyes half
critical and half amused the throng of dancers circling gaily to the
strains of three violins and a tinkling piano which did duty for an
orchestra when the youth of Fenways amused itself with a dance.

Dick was wholly and entirely a product of the war.  The lithe, slim
body, hatchet face, and keen, resolute eyes stamped him from head to
foot with the unmistakable _cachet_ of the airman.  He smiled, as he
watched the dancers, in acknowledgment of the gay greeting flung to him
by a score of laughing girls who, with the joy of youth, were giving
themselves unreservedly to the pleasures of the fox-trot.

Dick was a general favourite, and more than one pretty girl in the room
would have been only too glad to arouse something more than a passing
interest in the young airman, whose dare-devil exploits above the German
lines in France had brought him the Flying Cross, whose brilliant career
had been cut short by a bullet wound, received in a "dog-fight" above
Bethune, which had rendered him unfit for the continual hardships of
active service.  He had been offered a "cushy" job in acknowledgment of
his services.  But Dick could not bear the idea of being "in the show"
and yet not of it, and had accepted his discharge with what philosophy
he could muster.

His chief asset was his amazing knowledge of motor-engines.  They had
been his one absorbing craze.  While in the Army he had studied intently
every type of engine to which he could gain access; he had read every
book on the subject upon which he could lay his hands, and even among
the expert pilots of the Air Force he was acknowledged as a master of
engine craft.

It was this knowledge of engines which had sent Dick into the motor
business.  He knew, of course, that he could have obtained a good post
with one of the big companies had he chosen to stay in London.  But his
nerves were still tingling from the stress of war, and he was still weak
from the after effects of his wounds.  So, for the sake of peace and
fresh air, he had invested a part of his capital in a small motor
business at Fenways.  If he was not making a fortune he was at least
living, and the keen Norfolk air was rapidly bringing him back to
health.

At times the longing for the old life, the rash and whirl of the city,
came upon him with almost overwhelming force.

Suddenly a cameo of his days in France leapt into his mental vision.  He
found himself once again staring, as in a mirror, at the slim figure of
a half-fainting French girl stealing through the dusk towards the
British lines.  A crackling volley of shots from the Boche lines
followed her, but by some miracle she came on unhurt.  Dick had been
sent up to the front to supervise the removal of a German plane of a new
pattern which had crashed just behind the trenches and had wandered into
the front line (where, of course, he had no business!), and it was he
who caught the exhausted girl in his arms as she dropped into the
British trench.

He had often wondered since what had become of Yvette Pasquet.  She had
stayed on in the little town where Dick's squadron was stationed, and
they had become good friends.  Dick had thus learnt something of her
tragic history.

An Alsatian, French to the finger-tips, Yvette had lived in London for
some years and spoke English well.  But she had seen her father and
mother shot down by the Germans on the threshold of their home, and she
herself had only been preserved from a worse fate by a young German
officer, who had risked his life to save her from his drink-maddened
soldiers.  Sweet and gentle in all other respects, Yvette Pasquet was a
merciless fiend where Germans were concerned; her hatred of them reached
a passion of intensity which dominated every other emotion.

How she had managed to get through the German lines she never quite
remembered.  Her father had been well-to-do, and before her escape after
the final tragedy, Yvette had managed to secure the scrip and shares
which represented the bulk of his fortune, and had brought them across
with her safely concealed under her clothing.

From that time forward she had been the brain of a remarkable
organisation which had devoted itself to smuggling from the occupied
regions into France gold, jewellery, and securities, which had been
hidden from the prying eyes of the Hun.

After his wound Dick had lost sight of her.  For many months he had lain
dangerously ill, and when he had recovered sufficiently to write, Yvette
had disappeared.

Dick's reverie was broken at length by a light touch on his arm.  "A
penny for your thoughts!" said a soft voice at his elbow.

Dick came to earth with a jerk.  The voice was that of Yvette herself!
And when he turned he found her standing beside him, smiling into his
face with the light of sheer mischief dancing in her brilliant eyes.
With her was a tall young Frenchman, obviously her brother.

"Yvette!"  Dick gasped in sheer amazement.  "What on earth brings you
here?"

"I came to look for you, my friend," was the quaint but sufficiently
startling reply in excellent English.  "But let me present my brother.
Jules--this is Mr Manton."

Dick, his head in a whirl, mechanically acknowledged the introduction.
Yvette had come to look for him!  What could it mean?

"We came down from London this evening," Yvette explained, "and are
staying at the `George.'  We soon found your rooms, and hearing you were
here decided to give you a surprise."

"You have certainly succeeded," Dick rejoined.  "But how on earth did
you learn I was in Fenways?"

"Well," said Yvette, "it's no mystery.  I happened to meet Vincent quite
by accident in Paris, and he told me where you were."  Vincent was an
old flying colleague, and one of the very few people with whom Dick had
cared to keep in touch.

"I have tried several times to find you," went on the girl, "but even
your own War Office didn't seem to know what had become of you after you
left the Army, and my letters were returned to me."

Then her manner changed.

"Dick," she said seriously, "I came down to see you on business--
important business.  I can't explain here.  I want you to come back to
Town with us in the morning.  My brother and I have a proposition to put
before you.  We want your help.  Will you come?"

Wonderingly, Dick consented.

"Yes," he said, "I shall be glad.  My assistant can quite well look
after things here while I am away."

"Very well," said Yvette, with a look of relief which did not escape
Dick, "that's settled.  Now let us enjoy ourselves."

Dick spent a sleepless night, crowded with old memories which kept him
wide awake.  Next morning he found himself with his two companions in
the train for London.  Arriving at Liverpool Street, they took a taxi
and were soon comfortably ensconced in a private room at a small but
exclusive West End hotel.

It was not until after lunch that Yvette opened a conversation that was
destined to exercise a powerful influence on Dick Manton's career.

"Now, Dick,"--she called him "Deek"--"before I say anything I must make
it a condition that under no circumstances will you ever mention what
passes between us.  I know I can trust you implicitly.  I am going to
make you an offer which you are absolutely free either to accept or
refuse.  It will surprise you, and you are entitled to a full
explanation.  But in case you refuse, not a word of our conversation
must ever pass your lips under any circumstances whatever.  Do you
agree?"

"Of course I do," replied Dick, wondering what was coming.

"Very well," laughed Yvette, "now I can tell you everything."

"You will remember," she went on, "what I was doing in France--smuggling
money and valuables out of the reach of the Germans.  Well, I am doing
the same thing still, but on a different scale and by different methods.
I dare say you know that there is an enormous amount of smuggling into
England; the heavy import duties have made it a very profitable game.
What you probably don't know is that it is mostly carried on by Germans.
There is a regular organisation at work, clever, secret, and highly
efficient.  But the chain, like every chain, has a weak link, and I
happen to have found it.  The head of the whole undertaking is Otto
Kranzler, of Frankfort.  You will remember him.  He was the commandant
responsible for the murder of my father and mother."

"I remember!"  Dick exclaimed.

"At the very moment Kranzler is in Paris, looking for an opportunity to
get into England with a wonderful collection of jewels, which formed a
part of those given to the mock-monk Rasputin by the late Czarina of
Russia and some of his wealthy female admirers.  Now, Dick, I want those
jewels, and I am going to have them?"

"But how?" queried Dick.

"Kranzler is in a serious difficulty.  So far as I can make out the
jewels were brought into Germany by a Bolshevik agent for disposal, of
course, against the German law.  Rasputin's jewels were liable to
confiscation, and by some means the German Secret Police got wind of the
affair.  Kranzler, however, was too quick for them, and slipped over the
frontier into France in the nick of time.  Now he is in a quandary.

"Under French law he has so far committed no offence, and cannot be
arrested.  But if he attempts either to deal in the jewels or to export
them he will find himself in trouble.  The French police are
wide-awake--of course, they got a tip from the Germans--and are watching
him as a cat watches a mouse.

"So there he is," she went on, "planted in an hotel with jewels worth at
least fifty thousand pounds, and unable to move!  His one chance is to
get the jewels away by a messenger.  He is clever and may succeed, but I
don't think he will.  He has already tried but without success.

"I have a plan.  I think I can get the jewels out of the hotel.  But
they must be brought to England, and there is the difficulty.  When
Kranzler loses them he can't make any formal complaint, but he will
certainly get out of France as speedily as possible; that will give the
game away, and the watch on the boats will be keener than ever.  I dare
not risk sending them by a messenger.  An aeroplane is the only chance.
And I want you to fly that aeroplane!"

Dick coloured painfully.

"But, my dear Yvette," he stammered, "you don't mean to say you
intend--?"

"To steal the jewels?"  Yvette completed the sentence.

"Yes," Dick admitted, horribly embarrassed.  He found it impossible to
associate Yvette with what appeared to him a piece of cold-blooded
larceny.

"I quite expected you to say that, Dick," Yvette replied.  "And perhaps
I should have thought less of you if you had said anything else.  But
surely you don't take me for a common thief?"  Without waiting for
Dick's reply, she went on: "Now, try to look at this affair through our
French eyes for a moment.  I'm going to have those jewels--at least, I'm
going to try.  Who am I hurting?  A German who robbed me of my father
and mother!  Would any Frenchman or Frenchwoman hesitate a moment?  He
is a thief and a murderer!  Whom am I benefiting?  Myself?  Not for a
moment; I wouldn't touch a penny of the money.  If I bring this off--and
I think I shall--there will be at least a million francs to help on the
restoration of the devastated regions of France.  Now, Dick, you helped
France once.  Won't you do it again?  I must have some one I can trust,
and I know no one but yourself.  It will be great sport to beat the
police of two countries," she added with a laugh.

Dick's imagination caught fire.  It was impossible to resist Yvette's
appeal.  He was more weary than he knew of his humdrum life in Norfolk,
and here was an adventure after his own heart.  His mind was swiftly
made up.

"I'm on, Yvette!" he said shortly.

To his amazement, the girl burst into a sudden passion of tears.

"On?  Dick--if you could only realise what it means to me!" she sobbed.
"I have been all through the smashed-up parts of France--everything,
even our churches, is smashed and broken and defiled.  The poor people
are working desperately to restore their old homes, and they only want
help to be happy again.  But France has no money, and Germany won't
pay--as every one foresaw except your British statesmen.  Do you think I
am likely to hesitate to rob a German thief when it means happiness for
hundreds of French men and women and children?"

He tried clumsily to comfort her, and at length she grew more calm.

"There is no time to be lost," she declared.  "We must get over to Paris
to-night.  I have lately learnt to fly, and my aeroplane is hidden a few
miles from Paris.  The real problem is to get hold of the jewels and
bring them safely out of the hotel.  Then the aeroplane can start at
once."

"But what about Lympne?"  Dick asked.  "You know all aeroplanes entering
England from the Continent must land at Lympne for identification and
customs examination.  And the jewels would certainly be found."

"You must not land at Lympne," Yvette declared positively.  "You will
have to get in unobserved and land somewhere away from any aerodrome.
You can abandon the aeroplane; that won't matter if you get through
safely."

"And leave it to be identified in a few hours' time by the engine
marks?" asked Dick.  "No, Yvette, that won't do.  And besides," he went
on, "there wouldn't be the slightest chance of getting through.  The new
wireless direction-finders would give me away long before I could even
reach the coast, and the Air Police would do the rest.  I should simply
be shadowed till I landed--or even shot down if I refused to land!  Four
smuggling planes were picked up last week by the new wireless-detectors,
and every one was captured."

"Then I don't know what I shall do," Yvette replied blankly.  "I thought
you would surely be able to slip over at night."

Then Dick, even against his better judgment, which warned him he was
taking on a foolhardy enterprise, sprang his great surprise.

"Well," he said, "perhaps I can help you, after all.  You know, in
Fenways I'm supposed to be only a motor-dealer.  Really, I have been
working for over two years quite secretly on a combination of aeroplane
and motor-car, and now I think I have got it about perfect.  You can
change the motor-car to a little monoplane in less than half an hour.
The wing struts telescope back into the body, so does the
propeller-shaft, and the blades fold back along the shaft."

"Have you really?" she gasped eagerly.

"Yes.  Best of all, I've got an absolute silencer on the exhaust; I've
run the engine at top speed on the ground and found I could not hear it
a hundred yards away.  So far I have only made one or two flights, but
they were quite successful.  It seats two in little cockpits placed one
on each side of the centre line where the propeller shaft runs.  Why
shouldn't we try to fly her over tonight?  I feel pretty sure we could
do it at ten thousand feet without the direction-finders knowing
anything about us."

"Excellent!" cried the girl.

"The great disadvantage is that I can't get any speed to speak of on the
ground.  I have had to make everything very light, of course, and I
fancy about twenty miles an hour, unless the roads were exceptionally
good, would be our limit.  We should have no chance of getting away if
we were chased on the ground--or in the air, for that matter--if we were
spotted.  We might fly over to-night and chance getting caught.  Of
course, I have my pilot's certificate, and if we were caught I could
easily explain that I was making a night flight and my compass had gone
wrong.  It wouldn't be a very serious matter the first time as, of
course, we should have nothing contraband.  If we got over safely we
could take the chance of coming back loaded."

Yvette had become suddenly radiant.

"Why, Dick!" she cried, "that's the very thing.  We simply can't be
caught.  And when we land anywhere we can be ordinary motorists.  It's
wonderful--wonderful!"

"Don't be too sure," replied Dick grimly.  "The Air Police are pretty
wide awake.  However, it's worth trying.  Now, shall we go to-night?
There's a train from Liverpool Street at six-twenty.  We shall get down
to Fenways by nine.  We shall have five miles to walk to the shed where
I keep the machine--of course, we daren't drive out--and we must manage
to reach Paris about dawn.  If we are too early I cannot land in the
dark, and if we are late people will be about and we shall run the risk
of being spotted."

Yvette promptly produced a small but beautifully clear contour map.

"There's your landing-place," she said, pointing to a large clearing
surrounded by thick woods.  "It's about fifteen miles from Paris, and my
own aeroplane is pushed in under the edge of the trees.  It is quite a
lonely spot in the forest a little to the north of Triel.  Of late years
the forest has been very much neglected and very few people go there.
An old farmer, who lives quite alone, grazes a few sheep in the
clearing, and I have, of course, had to arrange with him about my
machine.  He thinks I am an amateur flyer, and I have told him I am
making some secret experiments and paid him to keep quiet.  I flew the
machine there myself when I bought it from the Francois Freres, of
Bordeaux.  Of course, I had my papers all in order when I bought it."

"All right; that will do well enough," said Dick.  "We will go over
to-night.  Jules can go by the boat train."

A few hours later Dick and Yvette were standing in the shed beside the
strange motor-car, Dick rapidly explaining the system of converting the
machine into a monoplane.

"We must get off the ground as quickly as possible," he said.  "People
go to bed early in these parts, but there is always a chance of some one
being about, and I don't want to be caught while we are making the
change."

At a suitable spot on the road, the change was made.  It occupied Dick,
with Yvette's skilful help, just twenty minutes.

"We can do it in fifteen," he declared, "when you are thoroughly
accustomed to it."

As a matter of fact they did it in less on one memorable occasion some
weeks later when their pursuers were hot on their heels.

Soon they were speeding swiftly southwards.  Dick had set the monoplane
on a steep, upward slant, aiming to reach ten thousand feet before he
drew abreast of London.  Thanks to the clinging mist, they were soon
utterly out of sight from below, and Dick had to steer by compass until
they sighted thirty miles ahead, and slightly to their right, the great
twin beams of light which marked the huge aerodrome at Croydon.

Then Dick veered to the south-east, flying straight for Lympne and the
French coast.  After all, he argued, the bold course was the best.  No
one would expect an aeroplane on an illicit errand to venture right
above the head-quarters of the Air Police, and should any machine be
about on lawful business the noise of their engines would prevent the
detectors picking up the throbbing whirr of the propeller, which, of
course, could not be absolutely silenced.

Fortune favoured them.  As they drew nearer to Lympne, swinging in from
the slightly easterly course he had set, Dick caught sight of the
navigation lights of the big mail aeroplane heading from London to
Paris.  His own machine, bearing, of course, no lights, was far above
the stranger, the thunder of whose big engines came clearly up to them.
A couple of red flares from the big plane signalled her code to the
aerodrome, the searchlight blinked an acknowledgment, and the mail plane
tore swiftly onward.  Dick could not match its hurtling speed, but he
followed along its track, confident that he would now be undetected.

They swept silently above the brilliantly lighted aerodrome, then across
the Channel, and just as dawn was breaking detected the Triel forest,
and dropped lightly to earth almost alongside Yvette's machine.  By
eight o'clock the machine, now a motor-car, was safely locked up in a
disused stable in the Montmartre quarter of Paris, and Dick, Jules, and
Yvette were soon in deep consultation.

That evening, just as dusk was falling, a half-drunken coachman sprawled
lazily on a bench set against a wall in the deep courtyard of the "Baton
d'Or," a quiet hotel located in aback street in the market quarter of
Paris.  By his side was a bottle of _vin blanc_.  Before him, harnessed
to a dilapidated carriage, stood his horse, a dejected-looking animal
enough.

Directly over his head, at a window of a room on the third floor, two
men stood talking.  One of them was Otto Kranzler.

Two rooms away, on the same floor, a curious little drama was being
enacted.

Lounging on a sofa near the door was Dick Manton.  Yvette, on a chair
drawn near the window, faced him.

Yvette rang the bell, and the two were talking when a chambermaid
appeared.

"Coffee and cognac for two," Yvette ordered.

A few minutes later the girl reappeared.  She crossed the room with a
tray and set it on the table in front of Yvette.

As the maid turned Dick's arm was slipped round her, and a chloroformed
pad was pressed swiftly over her face.  Taken utterly by surprise, the
girl was too firmly held to do more than struggle convulsively, and in a
few moments, as the drug took effect, she lay a limp heap in Dick's
arms.

Snatching from a valise a chambermaid's costume and cap, Yvette swiftly
transformed herself into a replica of the unconscious girl.  Then
picking up the tray and its contents she silently left the room, having
poured a few drops of colourless liquid into each of the glasses of
brandy.

Kranzler was evidently in a bad temper.

"I tell you," he said to his companion, "there _must_ be a way out.
That infernal--"

There was a knock at the door, and a chambermaid entered with coffee and
liqueurs.  It was Yvette!

"Would the messieurs require anything further?" she asked as she set
down the tray.

"No, that's all for to-night," said Kranzler in a surly tone, as he
picked up the brandy and drained it with obvious relish.  His companion
followed suit.

Dick was sitting beside the unconscious girl as Yvette re-entered the
room.

"She's quite all right," he said, as he watched her narrowly for signs
of returning consciousness, "but I must give her a little more just as
we are leaving.  How did you get on?"

"Splendidly," said Yvette; "they noticed nothing, and I saw them both
drink the brandy as I left the room."

Ten minutes later Yvette re-entered Kranzler's room.  The two men had
collapsed into chairs.  Both were sleeping heavily.

Without losing a second Yvette tore open Kranzler's waistcoat and passed
her hand rapidly over his body.  A moment later she had slit open the
unconscious man's shirt, and from a belt of webbing which ran round his
shoulders cut away a flat leather pouch.

From her pocket she took a reel of strong black thread.  To one end of
this she fastened the pouch, and, crouching by the open window, pushed
the pouch over the sill and swiftly lowered it into the darkness.

A moment later came a sort of tug at the line, the thread snapped, and
Yvette let the end fall.  Then, with a glance at her drugged victims,
she snatched up the tray and returned with it to her own room.

Lying on the sofa, the chambermaid stirred uneasily.  She was evidently
recovering.  While Yvette swiftly discarded her disguise Dick again
pressed the chloroform to the girl's face.

A few moments later "Mr and Mrs Wilson, of London," were being
escorted by the hotel porter to a waiting taxi-cab.

They never returned.

In the semi-darkness of the courtyard the drunken coachman had stiffened
and leant back against the wall as a small, dark object lightly touched
his shoulder.  His arm, twisted behind him, felt for and found a slender
thread.  Held against the wall behind him was the flat leather pouch
which Yvette had lowered.  A moment later it was transferred to a
capacious pocket, and the coachman, staggering uncertainly to his horse,
mounted the carriage and drove noisily out of the yard.  No one paid the
slightest attention to him; no one realised that that uncouth exterior
concealed the slim form of Jules Pasquet, his nerves quivering with
excitement at the success of the Gay Triangle's first daring _coup_.

An hour later the Paris police took charge of an old horse found
aimlessly dragging an empty carriage along one of the boulevards.  About
the same time, from a forest clearing fifteen miles away from Paris, a
tiny monoplane rose silently into the air and sped away in the direction
of the French coast.

Kranzler left Paris the following day and returned to Germany.  He was
strictly searched at the frontier, of course without result, and the
puzzled French police never solved the problem of how, as they thought,
he had beaten them.  He had not dared to complain.  "Mr and Mrs
Wilson" were never even suspected, for by a strange coincidence some
articles of jewellery were stolen from another room that same night, and
when the drugged chambermaid told her story it was assumed that the
Wilsons were hotel thieves of the ordinary type.

A month later the _Petit Parisien_ announced in black type with a
flaring headline:

"An anonymous gift of one million francs has been received by the French
Government, to be devoted to the relief of the devastated regions of
France."

CHAPTER TWO.

A RACE FOR A THRONE.

Paris, keenly sensitive to political vibrations which left less
emotional centres relatively unmoved, was rippling with excitement.

The death of the aged King John of Galdavia had been followed by the
sudden appearance of a second claimant to the stormy throne of the
latter principality in the Middle East, and the stormy petrels of
politics, to whom international political complications are as the
breath of life, had scented trouble from afar, and were flocking to the
gay city.  For the moment, however, the rest of the world seemed to take
but little interest in the new problem.  It was generally felt that the
succession to the Throne of Galdavia was a matter for the Galdavians
alone, and only a few long-sighted individuals perceived the small
cloud, "no bigger than a man's hand," which threatened to darken the
entire political firmament.

Back in his quiet Norfolk home, Dick Manton had dropped into a state of
profound dejection.  The adventure of the Russian Jewels, with its wild
plunge into the thrills of the old life, had awakened an irrepressible
desire for action and movement which had lain dormant while his
shattered health was being slowly re-established.

Now, fully recovered, and in the perfection of physical condition, he
could only contemplate with distaste and aversion continued existence in
the humdrum surroundings of East Anglia.

But what was he to do?  Like thousands of others he felt that the
ordered life of civilisation, with every daily action laid out according
to plan, was for him impossible.  His was essentially one of the
restless spirits, stirred into life by the war, which craved action,
difficulty, and even danger.  Moreover his growing affection for Yvette
troubled him.

Yvette had been delicately brought up.  She was accustomed to luxury,
and Dick could only realise that his present prospects were such that,
even if he were sure she cared for him, a marriage between them must
entail such sacrifice on her part as he could not contemplate with
equanimity.

But, though dull, he had not been idle.  The brilliant initial test of
the new motor-plane, which he had fancifully christened "The Mohawk" had
stirred his ambition, and every moment he could snatch from business had
been devoted to thinking out and applying improvements.  Some of these
had been of real importance, and the machine had gained substantially in
strength and lifting power, as well as in speed both on the ground and
in the air.  He was also making experiments in gliding.

For some months he had heard little of Yvette.  A few brief notes had
told him she was well.  But that was all, and he felt a little hurt.  He
never dreamed that Yvette's feelings were singularly like his own; that
she, too, was the prey of emotions which sometimes alarmed her.  They
were, in fact, kept apart by Dick's shyness and poverty, and by the
French girl's profound pride and reserve.

Matters were in this stage when Dick, to his great surprise, received a
brief telegram from Yvette.

"Can you come to Paris? very urgent--Yvette," the message ran.

Dick left at once and next evening found him with Yvette and Jules at a
small hotel near the Gare du Nord.  After a cordial greeting Yvette, as
usual, plunged direct into the business in hand.

"Now, Dick," she said, "our last adventure was quite a success.  Are you
good for something more exciting and decidedly more dangerous?  Or," she
added mischievously, "is Norfolk and the motor business exciting and
dangerous enough for you?"

Dick laughed.

"To tell the truth," he replied, smiling, "I'm about fed up with both of
them.  You can count me in on anything short of murder."

"I hope it won't come to that," was Yvette's rejoinder, "but I admit you
may find your automatic pistol useful, perhaps indispensable.  But let
me explain.  You English don't take much interest in foreign politics,
and perhaps you haven't--in Norfolk--paid much attention to Galdavia."

"I read that King John has died," Dick rejoined, "but I didn't suppose
it made much difference."

"Just as I expected!" said Yvette, laughing.  "Well, it does; it makes
quite a lot of difference as it happens.  Of course it ought not to.  In
the ordinary way Milenko, the son of King John, should succeed
peacefully enough.  But he has done some foolish things, and he is not
too popular.  There is a strong party in Galdavia which professes to
object to the manner in which John was called to the throne.  You know,
of course, how it happened; he was summoned after his predecessor, King
Boris, was killed by a bomb.  Legally, of course, Milenko's claim is
unchallengeable.  But legality doesn't count for too much in Galdavian
politics, and a second claimant to the throne has appeared in the person
of Prince Michael Ostrovitch, whose title lies in the fact that he is
descended from a brother of Boris's grandfather.  He was only a boy when
John was chosen, and in any case he would have had no possible chance of
election, for Galdavian opinion then was overwhelmingly in favour of
John.  But there has been a change.  The change would not be enough to
cause uneasiness, but for the appearance of another and very sinister
influence," and she paused.

"We are convinced that Germany, for very obvious motives, is backing
Prince Ostrovitch," she went on.  "The scheme is being very skilfully
worked, and so far we have failed entirely to secure positive proof.  If
we could do so the plot would be at an end, for France and Great
Britain, and perhaps even America would intervene at once.  They would
never allow a German puppet to ascend the throne of Galdavia.  But they
would not interfere with a _fait accompli_, especially if Ostrovitch's
election were so stage-managed as to give it the appearance of a popular
movement."

"I quite see the point," Manton said, much interested.

"Now we have found out this much," she went on.  "Jules and I have been
working at the case for some weeks, and we have both been to Langengrad,
the capital.  The secret is there.  Bausch and Horst,"--she named two
well-known agents of the German Foreign Office--"are both there,
disguised and under assumed names.  We believe that a formal agreement
is being prepared between the Ostrovitch Party and Germany.  Now,
neither the Germans nor the Ostrovitch Party fully trust one another,
and each will seek to safeguard itself by documents which in the event
of treachery by either side would mean certain ruin.  I am convinced
that such a document either exists or is being drawn up, and we must get
hold of it if the peace of Europe is to be kept.  Now," she added
slowly, "I want you to come with me to Langengrad and get it!"

Dick sat silent for a moment.

"I want to ask one or two questions," he said at length.  "Do you mind
telling me how you come to be in this?"

"I expected that, of course," replied Yvette.  "The answer is simple
enough.  I have been working for a long time for the French Secret
Service."

"And why do you want me?"  Dick queried.

Yvette coloured.

"I didn't expect that, Dick," she answered slowly.  "I want you first
because I know you thoroughly, and secondly because I must have the
Mohawk.  If you decide to go we shall go in the Mohawk as motorists
touring for pleasure.  But if we succeed we shall certainly have to
leave Langengrad in a desperate hurry, and we should certainly find all
the roads blocked.  What chance do you think a motor-car, to say nothing
of such a conspicuous oddity as the Mohawk, would have of getting all
through Austria-Hungary and Germany, even if it got over the Galdavian
frontier, when so many people in Galdavia, Austria, and Germany would
have the liveliest interest in stopping it?  No, we must fly out of
Galdavia.  We cannot fly in, because our passports must be in order--but
we shall have to fly out."

Dick smiled, but made no comment.

"But remember this," the girl said, "if we arouse the slightest
suspicion it is a hundred to one we shall never return.  The French
Foreign Office cannot appear in the matter under any circumstances.  If
we succeed, it means a big reward; if we fall into Ostrovitch's
hands--!" and a shrug of Yvette's shapely shoulders ended the sentence.

"Very well, Yvette," exclaimed Manton.  "I'll go with you.  There's no
one to worry about me, anyhow, and I'm fed up with Norfolk.  When do we
start?"

"The sooner the better.  Is the Mohawk ready?"

"Yes," replied Dick.  "I can start half an hour after I get back."

"Then you had better go over by the air express to-morrow morning,"
replied Yvette, "and fly back to-morrow night.  I will meet you at the
old place ready to start.  You can leave all papers to me."

Then Jules took up the story and for a couple of hours Dick listened
carefully to the details of the organisation which Jules and Yvette had
set up in Langengrad, and he marvelled greatly at the extent and
thoroughness of the work which had been done in so short a time.

A few days later Dick and Yvette, under the names of Monsieur and
Mademoiselle Victor, sister and brother, crossed the German frontier in
the Mohawk in the guise of tourists motoring through Germany and
Austria-Hungary to Galdavia.  Their passports, prepared by the French
Secret Service and bearing all the necessary _visas_, got them through
without the smallest difficulty.  Speaking French really well, Dick had
no doubt that, outside France at any rate, he could safely pass for a
young French officer.  Jules had remained behind to carry out his share
of the campaign.

Dick drove steadily via Stuttgart and Munich to Salzburg, where he
loaded up the Mohawk with all the petrol she could carry for the last
stage of the journey.  From Salzburg he proposed to fly across the
mountains to Klagenfurt, where he hoped to pick up the line of the Drave
River and follow it to its confluence with the Danube.  From there a
brief trip by road would bring them to the borders of Galdavia.

It was a lovely autumn evening when the queer-looking motor-car left the
"Bristol Hotel" at Salzburg and slid along the road to Radstadt, the
"winter sport" resort.  Very soon a sufficiently lonely spot was reached
and from a smooth patch of moorland turf the Mohawk rose into the air
just as the full moon was rising above the great mountains.  The engine
was working splendidly and the Mohawk climbing swiftly into the keen air
travelled steadily until, just before midnight, Dick and Yvette sighted
simultaneously the lake at Klagenfurt and the silvery line of the Drave
stretching away to the eastward.

With nearly three hundred miles to fly Dick set the Mohawk on a course
parallel to the Drave and slightly to the south of it, and for hour
after hour they flew on through the brilliant night.  Five thousand feet
up, they had no fear of detection and gave themselves up to enjoy the
beauty of the glorious panorama unfolded below them.

In less than five hours the Danube was sighted and crossed, and just as
dawn was breaking, the Mohawk came to earth a few miles from the little
town of Neusatz.  Quickly the aeroplane was metamorphosed into a
motor-car and the "tourists" ran into Neusatz, the little Danube town,
for breakfast and rest.  A few hours later they were across the borders
of Galdavia and heading for Langengrad, the old capital surmounted by a
frowning fortress built by the Turks in the Middle Ages.

Twenty-five miles from the city they halted at a wayside inn.

"This is where we shall meet Fedor," Yvette explained.

It was not until after they had had dinner, a homely meal in the true
Galdavian fashion, and it grew dark, that they heard from the roadway
three sharp blasts on a motor-horn.

"There he is!" exclaimed the shrewd athletic girl.  "Get the car out,
Dick!"

The latter hurried to the shed at the rear which served as a garage and
when, a few moments later, he drove the Mohawk into the white dusty
roadway he found a big touring car drawn up and Yvette talking to a
tall, dark-eyed young fellow whom she introduced to Dick as "Count Fedor
Ruffo."

Dick gazed at him with quick interest, for he had heard much of a
wonderful invention of the Count which was expected to play an important
part in their quest.  Fedor was a young fellow of quiet demeanour, with
the long nervous hands of an artist, a delicately cultured voice and
soft dreamy eyes.  Dick took him for an Austrian, which he afterwards
found to be correct.  He had taken a high degree in science at Vienna
and had settled in Langengrad as a teacher at the University there.

"Follow the Count's car as closely as possible, Dick," said Yvette.  "We
want to slip into Langengrad unnoticed, if possible.  The fewer people
who see the Mohawk the better."

The Count's car moved away almost noiselessly into the darkness.
Several times Fedor stopped and listened intently, and once they waited
an hour at a point where two roads crossed.  Nothing happened, however,
and about one o'clock in the morning they reached the outskirts of
Langengrad.  Here the Count left the main road and slipped into a series
of crooked by-streets lit only by the light of the moon.  Finally, he
turned into the courtyard of an old-fashioned house standing in its own
grounds and the Mohawk was speedily backed into a large empty shed, and
the door locked.

"Now, Mr Manton," said the Count in fair English, "will you drive Miss
Pasquet in my car to the Continental and register there?  She knows the
way.  Rooms have been taken for you.  You had better use my car while
you are here.  In the meantime if we meet in public remember we are
strangers.  Foreigners here are pretty closely watched."

The Hotel Continental at Langengrad is one of those cosmopolitan
caravanserais dear to the heart of the tourist.  As usual it was
crowded, and even at two o'clock in the morning the cafe was humming
with activity.  Consequently Dick and Yvette arrived almost unnoticed.
Explaining that they had been delayed by a motor breakdown they were
soon in their rooms and were sound asleep.

Next morning Yvette took Dick out into the gay pleasant city of
boulevards and handsome buildings.  He was immensely interested in the
brilliant scene, but he realised they were on a desperate mission and
took care to fix firmly in his mind the roads they would have to use.
It was necessary, of course, to keep up the appearance of being mere
gaping sightseers and they went from shop to shop buying a quantity of
souvenirs which neither desired in the smallest degree, and arranging
for them to be delivered to their hotel.

In the Balkanskaya, one of the principal streets, Yvette paused at last
before a jewellers' window which blazed with gems.  A moment later,
followed by Dick, she slipped into a narrow passage at the side of the
shop and turning into a doorway began to mount a flight of stairs which
seemingly led to suites of offices in the upper part of the building.
On the third floor she halted before a dingy door, and knocked softly.

Instantly the door was opened by Fedor who, inviting them within, shut
the door and locked it.  "Well, Fedor, what luck?"  Yvette asked.

"The best," was the reply.  "We have been able to find out exactly the
people with whom Bausch and Horst are associating, and where their
meetings are being held.  You have arrived in the very nick of time.  I
fancy--indeed, I am almost sure--the agreement will be signed either
to-night or to-morrow night.  I have overheard most of their talk."

"But how have you managed that?"  Dick asked eagerly.

"Miss Pasquet's telephone, of course," said Fedor.  "Didn't she tell you
about it?"  Yvette blushed and laughed.

"You didn't know I was an electrician, did you, Dick?" she said.  "Well,
you will soon see my little invention at work.  But it is nothing to
compare with Fedor's."

The good-looking Count talked earnestly for half an hour, acquainting
them fully with the work of Yvette's agents in the Galdavian capital,
until Dick became amazed at the perfection of the organisation which the
alert young French girl had so swiftly created.

"Ostrovitch's Party," Fedor concluded, "usually meet at the house of
General Mestich, who, as you know, is the Commander of the Headquarter
Troops in Langengrad.  He is a wonderfully able man, but is a confirmed
gambler and _bon viveur_, and is head over ears in debt.  He plays at
the Jockey Club each night.  There can be no doubt whatever that he has
been bought by Germany.  His house in the Dalmatinska for a long time
has been notorious for its rowdy parties, and as a result it is quite
easy for the conspirators to meet there without attracting undue
attention.  I am certain the Government does not realise how far things
have gone yet.  There is not a scrap of direct evidence.  Mestich is
personally very popular, and would in any ordinary matter carry with him
a big volume of public opinion.  But he dare not, as yet, venture on any
direct revolutionary action.  His hope is to give his plot some
semblance of a popular movement, and he is gradually winning important
adherents.  If he is given enough time I think he will succeed.  But
without Bausch and Horst--that is without Germany--the plot must go to
pieces.  They are finding the money, which is being spent like water."

"This is certainly interesting," Dick exclaimed.  "What are your
intentions?"

"Well, immediately opposite Mestich's house is an old building which for
many years has been used as a store.  It belongs to a loyalist friend of
ours, and I can use it as I like.  From one of the upper windows it is
possible to see right into Mestich's little _salon_, where the meetings
are held.  We will meet there to-night.  You must come separately to the
alley at the back; we dare not enter by the front.  There is a small
doorway there, half overgrown by clematis and apparently never used.  I
will be inside waiting to open the door when you knock."

For the rest of the day Dick and Yvette were careful to behave as
ordinary tourists "doing the sights" of Langengrad, the Rathaus, the
Museum, and the Opera House, and still buying piles of useless
souvenirs.  But they were soon to realise that a careful watch was kept
on all strangers in Langengrad.

Just as they were finishing dinner that night they were approached by an
officious little black-moustached man who sent a waiter to call them
aside.  When they were in a small smoking-room he made a courteous
request for their papers.  These were, of course, in order, and Dick had
no misgivings on the point.  But for some reason the shrewd,
sallow-faced official seemed suspicious, and Dick noticed with anxiety
that he spoke faultless French.

Would his own, he wondered, pass muster?

"Monsieur speaks French like an Englishman," the police officer suddenly
rapped out.

Luckily Dick was prepared.

"Yes," he answered readily, "I was brought up in England.  I was at
school at Rugby.  My friends in our French Air Force nicknamed me `The
Englishman.'"

The officer, it appeared, had also been an airman and proceeded to talk
interestingly on the subject of aero engines.  He was perfectly
courteous, but none the less Dick had an uncomfortable suspicion that he
was beneath a human microscope.  Fortunately the subject was on one
which he could not possibly be "stumped" and try as he would the police
official found he had met his match.

Dick was intensely interested and amused by his skill and courtesy.
None the less the position was most dangerous.  He realised fully that--
as was indeed the fact--the officer might be one of Mestich's
lieutenants, and unless he could be satisfied their chances of getting
away from Langengrad were trifling.

At length he seemed satisfied that Dick was really what he pretended to
be, and finally left them with a courteous farewell, having accepted a
glass of slivovitza--or plum gin--the liqueur of the Galdavians--and
chatted for a time on ordinary topics.

"That man is dangerous, Dick," whispered Yvette when he had gone.  "We
shall have to be most careful.  I wish I knew how much he knows, or
suspects."

They were soon to learn how acute this visitor really was!

Shortly after, Dick, smoking an exquisite cigarette such as can only be
bought in Langengrad, a dark coat thrown over his evening dress, left
the hotel quite openly, but keenly on the alert.  He suspected he might
be followed, a premonition that was to prove useful.

He strolled idly through the broad Kossowska agog with evening life,
gradually working his way towards the rendezvous, and keeping a sharp
look out.  Soon he picked out the figure of a man who always seemed to
be about fifty yards behind him.  A few turns through side streets
confirmed his suspicions; clearly, he was being "shadowed!"

Dick Manton's brain always worked rapidly in a crisis.  Obviously the
man must be got rid of.  So he speedily formed a plan.

Strolling down the alley behind the old storehouse, Dick marked the
exact locality of the clematis-grown doorway, passed it and then turned,
so timing his movement that he and his pursuer met exactly outside the
door.  It was the agent of political police who had interrogated him
after dinner!

Further pretence was useless, and Dick came straight to the point.

"To what am I indebted for Monsieur's very polite attentions?" he
demanded bluntly.

The stranger shrugged his shoulders insolently.

"Langengrad at night is not too healthy for foreigners," he replied with
an obvious sneer, "and of course we feel responsible for--"

He got no further.  Dick's clenched fist jerked upward with every ounce
of his strength and skill behind it.  Taken utterly by surprise the
police agent was caught squarely on the point of the jaw and went down
like a log.

Dick tapped at the door, which was instantly opened by Fedor, and
together they dragged the unconscious officer inside.  A moment later he
was securely bound, gagged and blindfolded.

Dick was now thoroughly alarmed about Yvette.  Would she be followed,
and if so, could she win clear?

Here fortune favoured them.  Apparently the police official, whatever
his suspicions were, had meant to make sure of Dick, knowing that Yvette
alone could not escape him.  A few minutes later they heard her knock,
and soon all three were in the house.

"Safe enough now," said Fedor laconically as he led the way through
piles of stored goods to an upper room at the top of the building.

The room was faintly illuminated by a gleam of moonlight which came
through a skylight in the roof, and when a small lamp was turned on Dick
looked around him with keen interest.  Filthily dirty, and apparently
unused for years, the room was crammed with a heterogeneous mass of
canvas packages and wooden boxes.  The only window was covered with
shutters through which circular holes had been bored to admit light, but
these were covered over with flaps of felt.  The dust of years lay thick
everywhere.

Dick's attention was instantly centred on a large, square table in the
middle of the room.

Upon the table stood what appeared to be a big camera, its lens pointing
to the window, with a screen of ground glass at the back of the camera
exposed.  A few feet behind, on a tripod, stood a small cinema apparatus
with the lens aperture directed at the ground glass plate of the camera.
To each ran electric wires from a bracket on the wall of the room.  The
whole of the electrical apparatus was weird and complicated.

There were also on the table two head telephones connected by wires to
the horn of what looked like a large phonograph.

"Now, Mr Manton," said Fedor in a low, intense voice, "I will show you
my new apparatus.  Mademoiselle Pasquet knows about it."

Dick was breathless with excitement.  Yvette's story of Fedor's
wonderful invention had filled him with keenest curiosity.

"If you will look through one of the holes in this shutter," Fedor went
on, "you will see, directly opposite, the window of Mestich's
dining-room.  The curtains are drawn, but you will see the room is
lighted inside.  He and his friends have been there for some time;
apparently they have been awaiting Horst."  Dick looked through the hole
and saw the lighted window.  "Now, come and look at the screen," urged
the Count.

As he spoke he touched an electric switch.  Immediately a soft purring
noise came from the camera and on the screen there showed a vivid
well-focused picture of a room with about a dozen men seated round a
long table.  The interior of the closed room was revealed by the new
invention.  At the head of the table, facing the camera, sat a big,
soldierly man whom Dick at once recognised, from his published
photographs, as General Mestich.

Fedor rapidly named the others--Bausch, Horst, Colonel Federvany, leader
of the Parliamentary Opposition, several officials of the Galdavian
Government and War Office, and two or three Jew financiers, one of whom
named Mendelssohn Dick knew to be of international reputation.

The marvellous picture was framed in a solid black outline.  It gave a
curious effect, just as though one were looking from the darkness into a
fiercely lighted cave.

Dick was almost stupefied with astonishment.

"Do you mean to say that that is the room in the house on the opposite
side of the road?" he asked.

"Certainly I do," said Fedor with a grim smile.

"But how is it done?" demanded Dick, aghast.  "The shutters are closed
here and the curtains drawn on the other side."

"It's a new electric ray I stumbled upon quite by accident," Fedor
explained.  "I was experimenting, and found it.  It passes quite readily
through wood, fibre and fabric, in fact through almost anything except
stone, mica, and metal.  That is why you see only part of the room; the
walls cut off everything except the space directly behind the window.
If the table were in the corner of the room they would be safe enough--
if they only knew!"

"Marvellous!"  Dick ejaculated.

"This new ray is projected from these two rods of silenium," the Count
went on, "and for some reason which I cannot explain it follows the
direction of the longitudinal axis of the metal.  Thus any object at
which the rods are pointed is rendered luminous by the ray on the
screen, which is coated with the barium sulphate used in X-ray work.  It
can be photographed by the cinema and we shall have evidence enough to
hang the lot."

Then he paused for a few seconds.

"Now we must begin," he said suddenly.  "They are just about to start.
Hold the telephone receivers to your ear.  Mademoiselle will look after
the cinema."

Picking up the receiver, Dick heard a voice speaking clearly and
earnestly.  It was evidently that of General Mestich, who, as he saw by
the screen, was on his feet and speaking.  The language, of course, he
did not understand, but Fedor, who was also listening, became excited
and snapped on a switch which started the phonograph.  In the meantime
Yvette was turning the handle of the cinema camera.

"Here it comes," Fedor ejaculated a moment later, and Dick saw General
Mestich take from his pocket a big blue document which he unfolded and
spread on the table before him.  Bausch at the same time produced a
similar paper.

Then Bausch got to his feet and also spoke briefly.  Immediately after
the documents were passed round and signed by all present.  The treaty
was made!  But every action of the plotters had been caught by the eye
of the camera, and every word they uttered was recorded by the
phonograph!  The evidence was complete!

"Now, Manton," said Fedor, "we have all we want except Mestich's copy of
the treaty which will be signed by the German Secretary of State, as
well as Bausch and Horst.  To get that and get away is your work.  I
have to stay in Langengrad and I dare not risk being seen and
identified.  You understand?"

"Of course," answered Dick.  "You have done wonders--absolute wonders!
But just tell me how this telephone works."

"That is Mademoiselle Pasquet's invention," replied Fedor.  "It is
really a secret change-over switch which projects an electric ray which
sets the General's transmitter working even when the receiver is on the
hook and the instrument would in the ordinary way be `dead.'  It can be
put in in three minutes; as a matter of fact I slipped it in one day
when I called to see the General and was kept waiting.  The main wire
from the General's 'phone to the Exchange passes over the house and it
was easy enough to `tap' it with a fine wire that can be pulled away so
as to leave no cause for suspicion.  I shall do that now; we shall not
want it again."

Soon after, the party opposite began to break up and finally, on the
screen, they saw the General standing alone, the treaty in his hand, and
a look of triumph and elation on his handsome face.  It was the picture
of a man who had very nearly reached the summit of his ambitions.  A
moment later he crossed to the big, high stove, lifted a heavy picture,
and slid aside a small door in the panelling of the wall.  This
disclosed a recess in which the treaty was deposited, the slide was
closed, and the picture replaced.

"Clever," said Dick, "but easy now we know.  I thought he would put it
in a safe.  But how are we going to get it?"

Yvette, who had been silent, interposed.

"I think the General's house might unexpectedly catch fire," she said
quietly.  "That will give Dick a chance to make a dash for the treaty in
the confusion."

"I don't see any better plan," Fedor agreed.  "It can easily be managed.
I have plenty of petrol here, and there is a small leaded window on the
ground floor that can be pushed in without making too much noise."

"Excellent!" exclaimed Dick.  "I'll manage that.  I'll see there's
plenty of confusion."

"Very well, that is settled," answered Fedor.  "Now I will take
Mademoiselle to your car and have everything ready for you to start.  It
will be touch and go.  Here is the phonograph record, with the cinema
film rolled up inside it.  Take care of them; they are priceless.  The
film must be developed in Paris."

Then Fedor produced a can of petrol and thoroughly soaked the room.

"This place is going up to-night," he explained.  "That police agent
will know all about it and it will be searched at once.  I can't get my
camera away and I don't want it found."

As he spoke Fedor was laying a long strip of fuse from the room to the
ground floor.  Striking a match he lit the end.

"In half an hour the place will be a furnace," he said coolly.

What to do with the police agent was a problem.

"I can't kill the fellow in cold blood," remarked Fedor, "and I can't
leave him here to be burnt alive."

Finally they dragged the man outside and left him lying in the darkest
corner of the alley they could find.

"Some one will find him when the fire starts," was Fedor's conclusion.

But some one found him much earlier, and their clemency nearly cost them
their lives!

Yvette and Fedor started for the Mohawk and Dick walked swiftly over to
the General's house.  It was very late and not a soul was stirring in
the now deserted streets.  Without difficulty Dick found the leaded
window and scarcely troubling about the slight noise he made, forced it
partly in, poured in a liberal supply of petrol and flung after it a
lighted match.  Instantly there was a most satisfactory sheet of flame.

A moment later Dick was hammering at the front door, shouting at the top
of his voice.  He aimed at making all the confusion he could.

Instantly the street was in an uproar.  People poured half-dressed from
the houses, and from General Mestich's residence came a stream of
frightened domestics, screaming in terror and half-choked with smoke.

Slipping unnoticed into the house, Dick made straight for the _salon_.
As he entered, General Mestich was in the very act of withdrawing the
treaty from the secret receptacle.  He turned towards Dick and their
eyes met.

Traitor though he was, the Galdavian General was a cool and brave man.
His hand dropped to his pocket and a revolver flashed out.  But he was
just a fraction of a second too late.  Dick's hand was ready on his
automatic, and as the General's revolver came out Dick fired from his
pocket and the leader of the Galdavian revolution fell dead with a
bullet through his heart.

A moment later Dick, the precious treaty in his pocket, had joined the
shouting throng in the crowded street.  As he did so, a burst of flame
from the old storehouse announced the success of Fedor's plan and added
to the general confusion.

Dick worked himself clear of the crowd and dashed off at top speed for
the Mohawk.  Yvette was already seated at the wheel, with the engine
started ready for instant departure.  As Dick sprang into his seat Fedor
laid beside him a loaded rifle.

"Ten shots, explosive bullets," he said coolly.  "It may be useful if
you are followed."

Then hastily they shook hands and the Mohawk leaped forward for the hill
road and safety.

The moon was unfortunately very bright, and it was not until they had
gone five or six miles that Dick ventured to draw a breath of relief.

"We ought to be safe now," he said.  "We must find a place to fly from."

The words were hardly out of his mouth when the roar of a big car behind
them caught his ears.  They had forgotten the bound and blindfolded
police agent.

That very astute individual had been found and released by a passer-by a
few minutes after they had left the warehouse!  Frantic with rage and
determined to catch Dick at all costs, he had acted with wonderful
promptness.  His first step was to send out cars loaded with armed
policemen to block all three roads leading from Langengrad so that
Dick's motor should not get away.  Had he been found a few moments
earlier Dick and Yvette must have been hopelessly trapped.  But the
delay of a few minutes had given them a priceless advantage.

Looking back as the big car came swiftly on, Dick caught the gleam of
rifle barrels in the moonlight.  His plan was swiftly made.

At the top of a steep slope, where the road made a sharp curve and
dipped into a small depression, Dick bade Yvette halt.  Blessing Fedor's
foresight, he took the rifle from the car and in the shadow flung
himself down on the grass bordering the road.  For five hundred yards
below him the road stretched in a smooth unbroken descent.

As the pursuing car came into sight Dick took careful aim and fired,
aiming not at the men, but at the engine of the car.  His first shot was
low, and he saw a burst of flame as the explosive bullet struck the road
a few yards short of the car.

His second shot got home.  The big car lurched, slewed round, and
dashing into the side of the road, toppled over.  Evidently the
explosive bullet had wrecked the steering gear.

He leapt into the car again, but the danger was not over.  Checked by
the steep rise the big car was only going slowly, and the men inside had
evidently escaped unhurt.  And they were clearly well led, for a dozen
of them dashed into the road and a volley of shots rattled round Dick as
he dashed for the Mohawk.

For the moment, racing down the hill, they were safe.  But Dick saw,
with inward trepidation, that a little farther on the road rose again
and they would be a clear mark for their pursuers in the bright
moonlight.

His fears were justified.  Again a volley of shots rang out and bullets
pattered round them.  One smashed the wind screen, a second went through
Yvette's hat.  But they were untouched, and raced on.  A moment more and
they would be safe.  Then another volley rang out and Dick felt a
stinging pain in his left shoulder.  He had been hit by one of the last
shots fired!

They were now out of range and Yvette sent the Mohawk along as fast as
she dared until, a few miles farther, she left the high road and drove
across the smooth upland turf to the shelter of a small wood where they
could convert the car into the aeroplane.

Despite the danger of delay Yvette insisted on binding up Dick's
shoulder.  Luckily no bone had been touched, but he had lost a lot of
blood.  By a tremendous effort of will he managed to help Yvette until
the aeroplane was ready, and then climbing into his seat collapsed in a
dead faint.

When he came to his senses again it was daylight and the Mohawk was
flying steadily high above a carpet of white mist which hid the ground.
Yvette, crouched over the duplicate control lever, nodded and smiled.

"Better now?" she called.

"A bit rocky," laughed Dick.  "Where are we?"

"We ought to be about over Scutari according to speed and compass
bearings," was Yvette's reply, "but the mist has been baffling me.
Still, I don't think we are far out."

"How long have we been flying?" asked Dick.

"About two hours," Yvette responded, "and we have been doing about
seventy.  That should bring us very near the coast."

After a stiff dose of brandy and a mouthful of food Dick felt better.  A
few moments later he pointed downwards.

"Lake Scutari!" he remarked, as he recognised the long narrow sheet of
water at the head of which the ramshackle half-Turkish town stands.

The mist was already breaking as, at ten thousand feet elevation, they
swept out over the Adriatic and headed for the Italian coast.  Then
Yvette began a rapid call on the wireless set with which the Mohawk was
fitted and placed the head-telephones over her ears.

"Got him!  He's there all right!" she exclaimed triumphantly a few
minutes later.  "He answers `O.K.'"

It was Jules, who for three days had been cruising off Cape Gallo in a
motor-launch, ready to dash to their rescue if anything went wrong as
they crossed the Adriatic, and who was now heading in their direction as
fast as his engines would drive him.

Suddenly Yvette uttered an exclamation of alarm.

"Dick," she said, "our petrol is giving out.  There is none left in the
number four tank and five and six will only carry us about seventy
miles."

Evidently the bullets of their pursuers had pierced the tank which was
now empty and the precious spirit had drained away unnoticed.

The situation was now serious indeed.  Could they get to Jules in time?
A wireless message bade him hasten.

"Ten miles more, Dick," said Yvette at last, "and then I can make three
miles and the glide as we come down.  It's lucky we are so high; we
ought to do it."

Then seven or eight miles away a column of vapour rose from the water
ahead.  Jules had fired a smoke bomb to guide them!  Their petrol was
almost gone.  But as the engine flickered out and stopped Yvette, with a
cry of joy, pointed to a tiny dot on the sea which they knew was Jules
rushing to their help.  A rocket shot up from the launch.

"He sees us!" said Dick, as Yvette set the Mohawk on a flat downward
slant.  Two minutes later they struck the water with a mighty splash
just as the motor-launch tore up, flinging a cloud of spray into the air
as she rushed to their rescue.  They were safe and they had saved a
throne!  But the gallant Mohawk sank to the bottom of the Adriatic.

------------------------------------------------------------------------

There was no revolution in Galdavia.  With the damning evidence of the
film and the phonograph record the Allies acted promptly, and with the
traitor Mestich dead the plot went to pieces.  King Milenko rules to-day
over a contented, happy and prosperous people, and his early follies
laid aside has become a capable and popular ruler.  Fedor they never saw
again; he was killed in a motor smash a week after they left, and the
secret of his wonderful invention died with him.

CHAPTER THREE.

THE SEVEN DOTS.

In a cosy little house at Veneux Nadon, near Moret-sur-Loing, in the
great Forest of Fontainebleau, Dick, Yvette, and Jules were seated in
earnest conversation.  They made a remarkable trio.  Dick was
unmistakably English, Yvette and her brother as unmistakably French--the
girl dark-haired and dark-eyed, and with all the grace and vivacity
which distinguish Frenchwomen of the better class.  Her brother, quiet
and dreamy, lacked his sister's vivacity, but there was a suggestion of
strength and iron resolution in the firm mouth and steely eyes.

"It will be terribly dangerous, Dick," said Yvette, with an altogether
new note of anxiety in her voice.

"I suppose it will," replied Dick, "but,"--and his voice hardened as he
spoke--"I don't see what else we can do.  We cannot run the risk of
seeing a perfected helicopter in German hands.  It would be too fearful
a weapon.  We must get hold of the plans and destroy the machine,
whatever the risk may be."

Strange stories had come through the French Secret Service of a new and
wonderful type of aircraft which was being tested with the utmost
secrecy somewhere in the neighbourhood of Spandau, the great military
town near Berlin.  Of its precise character little was known or could be
ascertained, and even Regnier, the astute and energetic head of the
French Secret Service, had at length to confess himself utterly beaten.
His cleverest agents had been baffled; more than one was in a German
prison, with little hope of an early release.  In the meantime the
mysterious machine flitted about the neighbourhood of the great
garrison, always at night, appearing and disappearing under
circumstances which proved conclusively that it must be of a type which
differed widely from any yet known to the public.

"We must go, Dick," said Yvette, "and Regnier is extremely anxious that
you should help us.  His trouble is that while he has dozens of capable
men at his command none of them has a really expert knowledge of
aviation.  He thinks that if you once got a good look at the machine you
could form a complete idea of what it really is."

"Very well," said Dick, "we will look upon it as settled.  We must work
out a plan."

For many months Dick Manton had been working steadily and secretly at
Veneux Nadon under the auspices, though not actually in the employ, of
the French Secret Service.  He had offered the plans of the Mohawk to
the British War Office, only to be met with a reception so chilly as
effectually to discourage him from proceeding further in the matter.
Regnier, however, was a man of a different stamp from the British
bureaucrat--keen as mustard and with the saving touch of imagination
which is characteristic of the best type of Frenchman.  He had unbounded
faith in Yvette, who had for some time been one of his most trusted
lieutenants, and when, angry at the attitude of the British War Office,
she had given him a hint of what the Mohawk could really do, he had
offered Dick the fullest facilities for continuing his work.  Under the
circumstances Dick had felt that to refuse would have been absurd.

Veneux Nadon was a lonely little spot.  Here Dick, though only thirty
miles from Paris, found himself in complete seclusion, with a
well-equipped workshop in large grounds completely buried in the lovely
forest, and thoroughly screened from prying eyes.  Regnier had put the
matter to him quite plainly.

"You are an Englishman, Monsieur Manton," he had said, "and I will not
ask you to sell your secret to France.  But we are willing to bear the
expense of perfecting your invention on the distinct understanding that
when the time comes England shall have the option of sharing in it to
the exclusion of all other countries except France.  When you are ready
we will officially invite the British Government to send a
representative and will give them the opinion of coming in on equal
terms.  I do not think we can do more or less."

So it was settled, and for many months Dick and Jules had toiled on the
building of a new Mohawk whose performances far surpassed those of the
machine lost in the Adriatic.  It was now completed and its preliminary
tests had satisfied them that they had forged a weapon of tremendous
potency.

The machine was of the helicopter type.  The idea, of course, was not
new, but Dick had solved a problem which for many years had baffled
inventors whose dream it was to construct a machine which should have
the power of rising vertically from the ground and remaining stationary
in the air.

Driven upward by powerful propellers placed horizontally underneath the
body, the Mohawk was capable of rising from the ground at a tremendous
speed.  Once in the air the lifting propellers were shut off and the
machine moved forward under the impulse of the driving screws placed in
the front and rear.  These screws were the secret of Dick Manton's
triumph.  They were of a new design, giving a tremendous ratio of
efficiency.  In size they wore relatively tiny, but possessed far
greater power than any propeller known.  The machine itself was nearly
square.  The body was completely covered by the big, single plane,
measuring about twenty feet each way.  This was the outside size of the
machine and so perfectly was the helicopter controlled that Dick had
repeatedly brought it to earth in a marked space not more than
thirty-two feet square.

Fitted with the new silencer which Dick had discovered and applied to
the old Mohawk with such signal success, the engine was practically
noiseless.  At high speed the tiny propellers emitted only a thin,
wailing note, barely audible a few yards away.  Time and again Dick had
sailed on dark nights only a few feet above the house roofs of Paris and
had found that the noise of the ordinary traffic was amply sufficient to
prevent his presence being discovered.

To ensure absolute secrecy the various parts of the machine had been
made in widely separated districts of France, and had been brought from
Paris to Veneux Nadon, where Dick and Jules had carried out the erection
of the machine alone.  The very existence of the new aeroplane was
utterly unsuspected by the few villagers who lived in the neighbourhood.

Keenly interested in his work Dick had thoroughly enjoyed the peaceful
life in the depths of the beautiful forest.  He and Jules had become the
closest of friends, and with Yvette, whose winning personality seemed to
bind him to her more closely day by day, they made up a happy house
party.  They were looked after by a capable old peasant woman who was
the devoted slave of all three, but whose admiration for Yvette seemed
to rise almost to the point of veneration.

On the day following the conversation recorded above, they were
surprised to receive a visit from Regnier himself--an alert, dark-eyed
man who seemed seriously perturbed.

"There is no time to be lost," he declared.  "I hear to-day from Gaston
that he has managed to get a near view of the new German machine.  He
says it rose apparently from the flat roof of a house standing in its
own grounds outside Spandau.  He happened to be near and caught sight of
it just in time.  Of course it was dark and he could see no details.
But he is positive that the machine rose nearly straight up from the
flat roof at an angle far too steep for any of our machines.  That alone
is sufficient to show that the Germans have got hold of something new
and valuable.  He waited for a long time, and finally saw the machine
return.  He declares it landed again on the roof.  Evidently, Monsieur
Manton, they have found out something along the lines of your invention,
even if they have not actually got your secret."

"How far away was Gaston when he saw it?" asked Dick.

"It must have been at least a quarter of a mile," replied Regnier, "as
the grounds are very extensive.  Gaston dared not venture an attempt to
get inside; the high fence is utterly unscalable, and the two lodge
gates are always kept locked and there is a keeper at each."

"And he heard the engine?"

"Yes, he says so specifically," replied the Chief.

"Well," said Dick, "at any rate we are ahead of them to that extent.  If
it had been my machine he would not have heard the engine at all at that
distance."

"However," he went on, "it is evidently time we acted.  Now, Monsieur
Regnier, Mademoiselle Pasquet has told me what you want.  I am willing
to go.  But I shall have to take the Mohawk.  How are we to hide it?  I
can get over and back at night safely enough, but to hide the machine in
the day-time will be another matter."

"Gaston can arrange that," the Chief declared.  "You know he has a farm
a short distance outside, Spandau.  There is a big barn there with no
sides, and your machine can be easily dragged into it and concealed
during the day.  You know Gaston is passing as a German farmer.  He has
acted for years for us in this way and has never even been suspected.
But you could not stay long."

"Very good," said Dick.  "I think the best plan will be for Jules to go
by motor and for Mademoiselle to go separately by train.  They must find
out somehow exactly where the German plane is lodged and, if possible,
where the plans are likely to be kept, and I must act accordingly.  In
any case, there will be no difficulty in smashing up the machine, but
unless we destroy the plans as well they will be building another too
soon to suit us.  I will go to Verdun and wait there with the Mohawk
until the time comes for me to fly over."

Jules and Yvette left the next day.  Jules' car was quite an ordinary
one, but it had one important detail added.  In the hollow flooring was
cunningly concealed a small but powerful wireless telegraph set, the
power for which was supplied by the engine.  It was highly efficient,
but had one serious drawback; it could only be used while the car was at
rest owing to the necessity for running an aerial wire up some tall
structure, such as a building or a tree.  This, in a country where every
one was specially suspicious of spies, was a serious peril.

Three days later seven mysterious dots began to excite the ungovernable
curiosity of the wireless world!

Jules and Yvette, on arrival in Berlin, had taken rooms adjoining one
another at the "Adlon," the big cosmopolitan hotel which is always
crowded with visitors from every country under the sun.  Yvette posed as
a school teacher on an educational tour, but her position was one of
great danger.  It was impossible to disguise her face, and although she
had done what she could to destroy her French individuality by wearing
peculiarly hideous German clothes, there was the ever-present danger
that she would be seen and recognised by some of the many German agents
who during the war had learnt to know her features, and who had good
reason to remember her daring exploits in Alsace.

At the same time, in order to have a possible retreat in a humbler
neighbourhood, Yvette had hired a room in one of the mean quarters of
the town, putting in a few miserable sticks of furniture and giving out
that she was a sempstress employed at one of the big shops.

She and Jules had decided never to speak in public.  It was essential,
however, that they should be able to communicate freely, and through the
wall between their rooms Jules had bored with a tiny drill a hole
through which he had passed a wire of a small pocket telephone.  They
could thus talk with ease and with the doors of their rooms locked they
were absolutely safe from detection so long as they spoke in a whisper.

It was on a dark night, the sky obscured by heavy masses of clouds, that
Dick rose in the Mohawk from the Forest of Fontainebleau and headed for
Verdun.  A couple of hours' flying brought him over the fortress and he
descended in a clearing in a dense wood where he was welcomed by Captain
Le Couteur, the chief engineer of the military wireless station.
Covered with big tarpaulins, the Mohawk was left under the guard of a
dozen Zouaves, and Dick and Captain Le Couteur motored to the citadel.

Here the Captain took Dick directly into the steel-walled chamber deep
under the fortifications which was the brain of the defences of Verdun.
It was the nucleus of the entire system of telegraph and telephone wires
which, in time of war, would keep the commander of the troops in the
district fully informed of everything that was happening in every sector
of the defences.  The innermost room of all, where none but the Captain
himself had access, contained the secret codes which dozens of foreign
agents would have willingly risked their lives to possess.  Their
efforts--and they knew it--would have been in vain, for the chamber was
guarded day and night by a band of picked men whose fidelity to France
was utterly beyond the possibility of suspicion.

"Your messages have already started--the seven dots at intervals of
seven seconds," said Captain Le Couteur when they were comfortably
seated in the innermost room.  "I got half a dozen test calls last night
and everything seems to be working well.  I expect they are arousing
some interest, for operators all over Europe will be mystified.  There
will be another call about nine o'clock and in the meantime you had
better get some sleep.  I will call you if anything happens."

Dick stretched himself on a couch and slept peacefully.  Nine o'clock
found him with Captain Le Couteur seated in the innermost room at a
table covered with delicate wireless apparatus.  Turning a switch, the
Captain lit up the row of little valves, put the receiving set in
operation, and assuming one headpiece himself, handed another to Dick.

He placed his hand upon one of the ebonite knobs of the complicated
apparatus and slowly turned it.  Then he turned a second condenser very
carefully.

"We are on the ordinary six-hundred-metre wave-length now," the Captain
explained, "and shall remain so until we get our seven dots.  I am bound
to keep the machine so or I should miss other messages I ought to hear.
But we will change as soon as we get your signal."

Presently they came, sharp and clear, dot-dot-dot-dot-dot-dot-dot.
Immediately Captain Le Couteur made some swift adjustments.

"Now listen," he said, "we are on a three-hundred-and-fifty-metre
wave-length."

A moment later came three M's--three pairs of dashes.

"That's Code Five," said Captain Le Couteur.  "Now we shall get the real
message."

It came in what to Dick was a gibberish of letters and figures, but
Captain le Couteur wrote it down and then, decoding it, read it off with
the skill of the expert.  It ran:

  "M M M begins Have located the machine stop Apparently entirely new
  type stop Tell Manton to be ready stop M M M ends."

"That's our newest code," the Captain explained, "and this is the first
time it has been used.  Jules learnt it only just before he left.  It is
very unlikely that the message has been picked up by anyone else, as the
wave-length is quite low, but even if it was, no one could decipher the
code from such a short message.  They would want one very much longer,
and even then it would probably take at least a week or ten days of very
hard work by a lot of experts."

And he paused.

"I think it would be well now for one of us to be constantly here," he
went on.  "Perhaps, too, you would like to overhaul your machine so as
to have it absolutely ready to get away at a moment's notice.  My
fellows will give you any help you want and they are all absolutely to
be depended upon not to talk."

Dick soon had the Mohawk ready; indeed there was not much to do after
such a short trip as the flight to Verdun.  The rest of the day he spent
chatting with Captain Le Couteur, finding him a delightful companion and
full of enthusiasm on the subject of wireless, of which his knowledge
seemed boundless.  Dick felt he could never tire of admiring the
wonderfully ingenious devices which the other had invented and put into
operation in his underground fortress.

Several more messages, chiefly brief reports, were received from Jules,
always heralded by the seven dots and begun with the three M's which
signified the secret code number Five.  For a few hours everything
seemed to be going well.  Then, towards evening came graver news, which
on being deciphered, read:

  "M M M begins Much fear Yvette suspected stop Tell Manton to be ready
  instant action stop M M M ends."

It could only mean, they realised, that Yvette had been recognised by a
German agent and was being closely watched.  The position was dangerous.

Dick spent the next few hours in an agony of suspense.  But he could do
nothing.  His first instinct was to fly to Berlin.  But Le Couteur's
iron common-sense showed him clearly enough that to do so would be
futile.  To keep the Mohawk in Germany, even for a single day, would be
risky; to try to hide her there for perhaps a week till they got a
chance to rescue Yvette would be suicidal.

A sudden swoop, swift and relentless action, and a quick escape were the
essentials of success.

Captain Le Couteur was scarcely less anxious than Dick himself.  He had
known Yvette since she was a child; they came from the same town in
Alsace.  But he possessed a brain of ice and restrained Dick's
impetuosity, though guessing shrewdly at its cause.

"The time is not come yet," he declared.  "This is a bit of business
which must go to the last tick of the dock.  Mademoiselle herself would
never forgive us if we spoilt everything by undue precipitation, and,
after all, Monsieur Manton, France is of even more importance than
Mademoiselle Pasquet, much as I admire her."

"I know," Dick admitted.  "But when I think of her, with her war record,
which they know all about, falling into the hands of those brutes, I can
hardly sit still."

"They have not got her yet and she is very clever," replied Le Couteur.
"Let us hope that she will give them the slip."

But about ten o'clock the following morning the dreaded blow fell.

They were seated in the underground chamber, Dick ill at ease and full
of gloomy forebodings.  The apparatus set to receive messages on
three-hundred-and-fifty-metres.  Suddenly a buzzing noise was emitted
from the loud-speaking telephone on the bench.

Seven dots, seven times repeated, clicked out strong and dear!

Surely seconds had never passed so slowly!  It seemed an age before
Captain Le Couteur, his face white as chalk, took down the message which
followed, and then referring to the code, read:

"Yvette arrested this morning by Kranzler."

Dick turned dizzy and the room spun round him as the dreadful
significance of the words struck him.  Kranzler, of all men!  The
murderer of Yvette's father and mother, the man whom she had beaten over
and over again at his own game of espionage during the war, the man
whose sensational attempt to dispose of Rasputin's stolen jewels had
been foiled by Yvette's skill and daring!  He was, as they knew, a
desperate brute who would stick at nothing to feed his revenge.

Dick was rushing from the room, determined at all hazards to leave for
Berlin at once, when Le Couteur seized his arm in a grip of iron.

"Steady, Manton," he said sharply.  "Don't be a fool.  You'll spoil
everything.  Sit down and wait for more news."

The words brought Dick to his senses.

"I'm sorry, Le Couteur," he said, "but I think I went a bit mad.  You
are quite right.  But Kranzler--of all men!  You know the story, of
course?"

Le Couteur nodded.

"It could hardly be worse," he admitted, "and there's no use disguising
the fact.  But we must wait for more from Jules.  In the meantime I am
going to talk to Regnier.  He must have more men on the spot.  At all
costs Mademoiselle must be rescued."

They were soon in touch with the Chief in Paris, who was horrified at
the news.

"I will get some more men over at once," he said.  "But we can do
nothing until we find out where they have taken her.  Jules will realise
that.  You are certain to get another message from him before long."

It was not until later that day that they learned how the arrest had
been effected.  Yvette, as soon as the position of the German plane had
been located, had managed in the guise of a girl seeking work, to scrape
acquaintance with one of the maids employed at the big house where the
aeroplane was lodged.  The girl had actually taken her up to the house
and Yvette had coolly applied to the housekeeper for employment.  There
was, as it happened, no vacancy, but Yvette had used her eyes to good
purpose.  In the walk from the lodge to the house and back she had
caught sight of the shed in which, obviously, the aeroplane was housed,
and had noted its exact position in the extensive grounds.  Hurrying
back to the hotel she had communicated this information to Jules and
both were filled with excitement at the important step forward they had
made.

Sitting in the lounge of the "Adlon" next morning Jules had seen
Kranzler enter.  He had started at once to warn Yvette to "lie low," but
was just too late.  Yvette at that moment came down the staircase and
before Jules could interpose had met Kranzler face to face.  She was
instantly recognised.

With a grin of delight on his evil face the big German bowed profoundly.

"This is indeed a pleasure, Mademoiselle Pasquet!" he said ironically.

Yvette very coolly tried to carry it off.

"Monsieur has, I think, made a mistake," she said in German.

"It's no use, Mademoiselle," was the harsh reply, "I know you perfectly.
You must come with me--or shall I call the police?"

There was obviously nothing for it but to obey, and Yvette was forced to
leave the hotel in the clutches of the one man in all Germany she had
the greatest reason to fear.

Jules acted promptly.  Slipping out of the hotel he hurriedly wheeled to
the front a motor-bicycle he had hired to enable him to travel speedily
between Berlin and Spandau.  He got round just in time to see Kranzler
put Yvette into a taxi, and followed them until they alighted at the
door of the house in the Koeniggratzer-strasse which was the
head-quarters of the German Secret Service.  Yvette was taken inside.

To get the news to Dick was now Jules' first consideration.  Knowing
something of the methods of the German Secret Service he was reasonably
sure that Yvette would be put through a long examination before she was
taken to prison, and he decided to run the risk of being absent for a
short time to get his message away.  He drove hastily in his car out
into the country until he found a tree to which his aerial wire could be
attached and got off the brief message which conveyed the news to
Verdun.  Then he returned to watch, and ascertain where Yvette was to be
imprisoned.

The taxi was still outside the door when he got back to the
Koeniggratzer-strasse.  As an excuse for waiting he feigned engine
trouble and tinkered with his machine, keeping all the time a close
watch on the door opposite.

He had not long to wait.  In about half an hour Yvette was brought out,
still in the custody of Kranzler, and driven away.  Jules followed, and,
at length, had the satisfaction of knowing that Yvette was in the big
prison outside Spandau.  It was a melancholy satisfaction, it is true,
but to know where she was was of supreme importance.

Driving to Gaston's farm he soon informed Verdun where Yvette was
located and then turned to discuss the position with Gaston.

To his intense surprise and delight, Gaston was able to give him some
comfort.

"Of course, it is a great misfortune," he said, "but it might be worse.
They have taken her to the one prison in Germany where we have been able
to keep a thoroughly trustworthy agent.  He is a warder who passes as
Herman Fuchs; his real name is Pierre Latour.  We shall soon know all
about Mademoiselle."

The front of the prison was in dear view from Gaston's farm.  Going
outside, he called on Jules to help him to move one of three large
barrels, each containing a big flowering shrub, which stood side by side
in front of the house facing the prison.  One of these was taken away,
leaving only two.

"We shall have Pierre over here this evening," Gaston chuckled.  "That's
the signal that I want him."

Sure enough, soon after dark, Pierre appeared.  A few words explained
the situation.  He was off duty now for the night and free to do as he
pleased.

"Leave it to me," he said.  "I will be back in an hour."

He returned with a rough plan of the section of the prison in which
Yvette was confined.  Her cell occupied a corner on the first floor at
the head of a flight of steps leading down to the big courtyard.  If
Yvette could get out of her cell it would be an easy matter to reach the
door leading to the yard.  But to get over the high wall, quite
unclimbable, was a difficult problem.  The entrance from the roadway was
always guarded by two warders who occupied little separate lodges placed
one each side the gateway.

"I can get her out of her cell," said Pierre, "but how to get her out of
the yard I don't know.  I can get a false key to her during the day, but
if I were found in that quarter of the prison at night it would mean
instant dismissal.  On that point the rules are inflexible and we cannot
risk it."

"No," said Gaston, "it is absolutely essential that you shall remain in
the prison.  But I think I can see a way."

He crossed the room to an old-fashioned bureau and produced from a
drawer what looked like a heavy short-barrelled pistol.

"Gas!" he said laconically, "fire that at a man's face within five yards
and he will drop like a log.  It holds four shots and makes no noise.
If Mademoiselle can get this she can knock out the two men at the lodge
and easily slip out.  You can bring her straight here, and we can hide
her until she can get away."

"She cannot hide that in her cell," said Pierre, "but I can hide it in
the courtyard.  Write her a letter telling her exactly what to do and
where the pistol will be.  I can slip into her cell a skeleton key which
will open the door and also the door at the bottom of the steps.  But
you must manage the rest; I cannot do any more.  She must get out
immediately after the last visit of the warders at nine o'clock."

"Thanks very much, Pierre," said Jules.  "I can see no other way, and at
all costs we must try to get her out.  Neither my sister nor myself will
ever forget."

Speedily a letter was written which gave Yvette full details of what was
proposed, and Pierre was about to leave when Jules asked him if he had
heard anything of the secret aeroplane.

Pierre shook his head.

"There are a lot of privately owned aeroplanes about here," he said,
"but I don't know anything more than that.  I have seen the one you
refer to going up at night--the house is in plain view from my room on
the first floor of the prison--but I never heard there was any secret
about it, and there are so many aeroplanes about that no one takes any
notice of them."

Jules told him all they had found out, and of their suspicions, and
found Pierre was able to give them valuable information.

The aeroplane shed, he told them, was just where Yvette had located it.
Above it--and this was important--were some rooms which were used,
apparently, as offices.

"I have often," said Pierre, "seen a man come from the offices with what
looked like plans, make examination and measurements of the machine, and
then go back.  But I never took much notice; I had no reason to."

Pierre left, taking with him the letter to Yvette.  For an hour Jules
and Gaston discussed the situation.

"We must get her out to-morrow," declared Gaston, "or else they may take
her away and we shall not be able to find out where she is.  Manton
ought to fly over to-morrow night.  If we can get Mademoiselle Pasquet
out she can hide here quite safely for a few hours, but there will be a
very close search when her escape is discovered."

"I'll get the message to Manton at once," said Jules.

And so it happened that Dick and Le Couteur, who had been waiting for
hours in a state of tense anxiety, received a few minutes later the
call.

  "M M M begins To-morrow night stop Come early as possible stop Three
  lights in triangle safe stop Four keep off M M M ends."

"At last," said Dick grimly, with a look on his face that boded ill for
some one.  He looked drawn and haggard, and even Le Couteur could hardly
repress a shudder at the savage determination that blazed in his eyes.

For Yvette the next day was one of misery.  Time after time she was
dragged from her cell and taken before the Governor of the prison, and
Kranzler, to be pitilessly cross-questioned and even threatened with
violence.  But even though she knew well that the two brutes were quite
capable of carrying out their threats nothing could break the spirit of
the French girl.  To all their questions and menaces she turned a deaf
ear and nothing they could say would induce her to affirm or deny
anything.  Utterly worn out she was at length roughly bundled back into
her cell, where she dropped exhausted on the miserable apology for a
bed.  At least she was alone.

It was about five o'clock and she had fallen into an uneasy doze, when
she was awakened by a slight noise at the door.  She saw the observation
grille slide back and, pushed through the grating, a tiny parcel fell
with a subdued clink on the floor.  Then the grating was closed.

Hastily she sprang to her feet and seized the parcel, a new hope surging
in her breast.  It could only mean help!

Inside the parcel was a letter, unsigned of course, but in Jules'
handwriting, and a small key.

Nine o'clock came, and with all the wearisome ceremony dear to the
German heart, the guard, accompanied by a wardress, made its final
inspection for the night.  A few minutes after the big prison was as
silent as the grave.

Half an hour later Yvette cautiously fitted the key into the lock.  It
had been well oiled, and the door swung open without a sound.  Creeping
down the flight of steps Yvette found that the key also opened the door
at the bottom, and in a moment she was in the yard.

Rain was falling heavily.  There was not a ray of light in the yard
excepting a faint gleam which showed the position of the warders'
lodges.

Before leaving her cell Yvette had pulled her stockings over her boots,
and moving without a sound she groped her way along the wall.  A few
feet from the door she found the big stackpipe which brought the rain
water from the roof.  Stooping she lifted the iron grid of the drain and
thrust in her hand.  Her fingers closed on the butt end of the gas
pistol.

Silently, following along the wall in preference to crossing the
courtyard, she stole towards the lodge.  Complete surprise was
essential.

With the pistol ready in her hand, she softly opened the door of the
lodge on the right of the gateway.  Luck was with her again.  The two
men, in defiance of rules, were in the same lodge talking quietly.

The noise of the door opening brought them to their feet with a jump.
But they were too late.  Only ten feet away from them Yvette pulled the
trigger twice in rapid succession.  There was no more noise than a
slight hiss as the gas escaped and the two men dropped insensible.
Snatching up a bunch of keys from the table, Yvette herself
half-stifled, quickly got outside and closed the door.  A moment later
she had opened the wicket-gate and slipped through.  She almost fell
into the arms of Jules and Gaston, and at top speed the three raced
through the rain for Gaston's farm.

Luckily, the pouring rain swiftly obliterated their footprints, but they
had hardly got into hiding, wet through but triumphant, when pandemonium
broke out in the prison, and the frantic ringing of the big bell
announced the escape of a prisoner.  The two warders, of course, had
speedily recovered, and hastened to tell their story, and a quick search
had revealed that Yvette's cell was empty.  A few minutes later search
parties were hurrying in every direction in pursuit of the fugitive.

Gaston's farm, lying close to the prison, was naturally one of the first
places to be visited.  Gaston, smoking peacefully by the fireside, soon
heard, as he expected, the savage clamour of dogs in the farmyard
mingled with agonised cries for help.

He hurried out.  Two warders, one of them badly bitten, were backed
against the fence, hardly keeping at bay with their sticks a couple of
powerful dogs.

Gaston called off the dogs and, full of apparent solicitude, expressed
his regret.  He listened to the guards' explanation.

"She cannot have been here," he declared, "the dogs would have bitten
her to pieces.  But, of course, we will look round if you like."

The guards, however, were more than satisfied.  Gaston's argument was
backed by their own experience, and they were quite ready to be
convinced if they could only get away from the ferocious dogs who
continually prowled about snarling as though even the presence of their
master was hardly sufficient to protect his visitors.  They little
dreamed that the savage brutes would indeed have torn Yvette to pieces
had not Gaston thoughtfully taken the precaution to lock them up before
he and Jules started to rescue her!

Away at Verdun Dick stood beside the Mohawk waiting impatiently in the
dark.  Time and again he had tested every nut and screw in the machine;
time and again he had run the powerful engine to make sure that it was
in working order.

At last the longed for moment for action came.  Anything was better than
long drawn-out suspense.

He wrung Le Couteur's hand as he stepped into the machine.

"I'll be back with her by dawn," he said, "or else--" there was no need
to finish the sentence.

He had not gone five minutes before Le Couteur received a message from
Jules announcing that Yvette had escaped.  If only Dick had known!

It was raining hard when the Mohawk rose into the air, but Dick was
beyond caring for the weather, and anxious only for Yvette, he sent the
helicopter tearing through the darkness eastward to Berlin.  He drove
almost automatically, his thoughts intent on the girl ahead of him.

As he approached Berlin, the weather cleared and the rain stopped.  All
around him were the navigation lights of the German mail and passenger
planes, hurrying to every quarter of the Empire, and, even in his
anxiety, Dick was conscious of an uneasy feeling of irritation at the
thought that England was being left so far behind in the race for the
mastery of the air.

Then he caught sight of the great beams of light that marked the
position of the huge Berlin aerodrome, and a few minutes' flying brought
him above Spandau.  He circled twice, looking for Gaston's signals, and
at last he dropped lower, caught the gleam of the three lanterns which
Gaston had placed to guide him, and brought the machine swiftly down
beside the big barn.  Then he leaped from his seat.

He nearly gave a shout of joy that would have aroused every German
within a mile!  For there, in the light of the lanterns, stood Yvette
herself.

There was no time for explanation.

"Now's your chance," gasped Jules, wild with excitement, "the German
plane has just gone up!"

Dick's face hardened instantly.

"Get in, Yvette," he said curtly.

Yvette stared in utter astonishment.  This was a new Dick with a
vengeance!  All his usual graceful courtesy had dropped from him in the
instant; the sheer fighting spirit was on top and Dick was, for the
moment, the officer giving commands to his subordinates.  His face was
set like granite, and into the keen eyes there came a look Yvette had
never seen there before.  The cheerful, laughing "pal" had gone; in its
place stood the fighting machine, pitiless and efficient.

For an instant the girl was almost on the edge of rebellion; then she
turned, and, without a word, took her place in the machine.  As she did
so, she caught Dick's eye.  For an instant the stern face relaxed; then
the iron mask shut down again.

For five minutes, while Yvette put on her leather helmet, Dick studied
the plan which Jules showed to him by the light of a shaded lantern.
When the Mohawk jumped into the air every detail of it was photographed
indelibly on his brain.

For three thousand feet the Mohawk shot upward at a speed which left
Yvette dizzy and breathless.  Then they hung motionless, as Dick peered
anxiously earthward.  Were they high enough?

With a smothered exclamation Yvette pointed downward.  Far below them a
light was circling swiftly, darting hither and thither like a will o'
the wisp.  No mail plane would behave like that.  Dick decided that here
was his quarry.

Silently the Mohawk came down till it was not more than five hundred
feet above its unsuspecting prey, the loud drone of whose engine came
clearly on the air.  Dick swung round in a circle, following every
movement of the machine below, with a swift precision which Yvette
keenly appreciated.

Dick had made up his mind that the offices above the aeroplane shed
probably held the key to the problem they had to solve.  He knew he
could destroy the machine itself.  But that would not be enough if the
plans remained intact; a new machine could quickly be built.  If he
could destroy the plans, on the other hand, there would be at least a
lot of delay, which would enable the French agents to perfect their
plans for discovering the secret.  In all probability, he reasoned, the
office would serve as the draughtsmen's workroom, and if this were so, a
well-placed bomb might destroy the labour of months.

So he watched and waited, until at length they saw the German aeroplane
going home.  It came down in a wonderfully steep descent which was
enough to tell Dick that the Germans had indeed made a discovery of
great importance, and landed so slowly that Dick could hardly believe
his eyes.  But, at least, he saw enough to be sure that the descent was
not the vertical drop of his own helicopter.  His secret remained his
own!

Close beside the shed a couple of hooded airmen alighted.  Lights were
switched on and they began a careful examination of the machine.  Five
hundred feet above Dick watched the figures with interest.

Suddenly the men below stiffened and looked skyward, listening intently.
Evidently they had caught the faint sound of Dick's propellers.

A glance through his bomb sights showed Dick that he was in the position
he desired.  There was now no possible escape for the craft below.

Then one of the men pointed upward.  Even in the darkness he had caught
a glimpse of the Mohawk.

Dick's hand shot to the bomb controls and he pulled a trigger.  A petrol
bomb fell squarely on the German plane and burst with a soft explosion,
barely audible.

A sheet of fire followed, and in an instant the German plane was a mass
of flames, fed by the petrol which streamed from its tanks.  One of the
Germans was caught in the outburst and apparently died almost instantly.

The second man, however, dashed into the office.  The Mohawk moved
forward a few feet and three more bombs fell in quick succession, right
on the roof of the shed.  Then, her work done, she rose high into the
air and Dick and Yvette watched the results.

The shed below them was already a furnace.  Apparently there must have
been some petrol tanks there, for no ordinary building could have burned
so furiously.  In a few minutes nothing remained but a heap of glowing
embers.

Dick watched keenly for the man who had run into the office, but he
never reappeared, and it was evident that, trapped by the flames, he had
been unable to get out in time, and had perished.  Dick little suspected
at the time how important the fate of that man was to prove.

Then Dick set the Mohawk at top speed for home.  Just as dawn was
breaking Verdun loomed ahead.  Yvette was saved.

Two days later the _Berliner Tageblatt_ told how the famous scientist,
Professor Zingler, had perished in a fire which had destroyed his
laboratory at Spandau.  The fire was attributed to an explosion of
petrol on the professor's aeroplane which had set light to the office.
Unfortunately, the paper added, all the professor's valuable papers and
books had been lost.

The secret of the Zingler aeroplane had perished, and the seven dots
were never heard again.

CHAPTER FOUR.

THE SORCERER OF SOHO.

"Unless we can solve this terrible mystery in the course of a few weeks,
it is hardly too much to say that England is doomed."

The speaker was the white-haired Professor Durward, the distinguished
head of the Royal Society.  He sat facing the Prime Minister in the
latter's room at 10, Downing Street.  Round the long table were grouped
the members of the Cabinet.  They were men who had lived through stormy
and troublous times and had met stories of disaster without flinching.
But, as they admitted afterwards, none of the terrible tidings of past
years, when the fortunes of the Empire seemed to be tottering, had
affected them to the same extent as the few brief words with which the
distinguished savant summed up the long deliberations on which they had
been engaged.  They seemed pregnant with the very message of Fate.
Almost they could see the writing on the wall.

"But, Professor," asked the Premier, "do you really mean that nothing
whatever can be done to check or prevent this terrible malady?"

"Nothing, so far as I am aware," was the reply.  "As you know the most
distinguished men of science in England have been at work on the
problem.  We had a very full meeting last night, and the unanimous
verdict was that the disease was not only absolutely incurable, but that
nothing we have tried seems capable of affording even the slightest
alleviation.  The deaths reported already amount to nearly half a
million; though the truth is being carefully concealed from the public
in order to allay panic, yet practically every community in which the
disease has appeared has been virtually wiped out.  Curiously enough it
does not seem to be spread by contagion.  In spite of the rush of
terrified people from districts in which it has appeared, no cases have
shown themselves except in towns or villages where the mysterious violet
cloud has been observed.  That phenomenon has been the precursor of
every outbreak."

A month before, in the tiny village of Moorcrest, buried in the recesses
of the Chilterns, an unoccupied house had suddenly collapsed with a
slight explosion.  No one was in the house at the time, and no one was
injured.  As to the cause of the explosion no one could form an idea.
Nothing in the nature of the remains of a bomb could be discovered, and
there was no gas laid on in the village.

But the few villagers who were about at the time spoke of seeing a dense
cloud of pale violet vapour pouring from the ruins.  On this point all
observers were agreed, and they all agreed, too, that the cloud was
accompanied by a powerful smell which strongly resembled a combination
of petrol and musk.  That was all the evidence that could be collected.
No harm seemed to follow and the matter was speedily forgotten.

Very soon, however, the incident took on a new and sinister
significance.

A week later a similar explosion took place in Ancoats, a poor and
densely crowded suburb of Manchester.  In every respect this incident
duplicated the happening at Moorcrest.  Naturally, it created something
of a sensation, and the papers, recalling the Moorcrest mystery, made
the most of it.

During the next fortnight similar explosions, all bearing the same
distinguishing features, occurred in various parts of England.
Sometimes there would be three or four in a single day in the same, or
closely adjoining, areas.  The public became excited.  Not a single
person was injured, the damage done was apparently trifling, since all
the houses destroyed were of the poorest class.  It looked like the work
of a maniac--purposeless and without the slightest trace of a motive.
People spoke of Bolshevists and Communists.  But what Bolshevik or
Communist, others asked, would waste time and effort to inflict such
absurd pinpricks on Society?

They were soon to be undeceived.  An enemy of Society was indeed at work
armed with a weapon of a potency which far outstripped the paltry
efforts of the Terrorists of old, to whom the bomb and the revolver were
the means of world regeneration.

The explosion at Moorcrest took place on May 2nd.

Twelve days later, on May 14th, Doctor Clare-Royden, who was in practice
at Little Molton, a village about four miles from Moorcrest, received an
urgent message from an old patient summoning him to Moorcrest.

Doctor Royden, jumping on his motor-bicycle, answered the summons at
once.  A terrible surprise awaited him.

Practically every inhabitant of the village, about a hundred people in
all, were in the grip of a fearful and, so far as Doctor Royden's
knowledge went, wholly unknown malady.

Its principal symptoms were complete paralysis of the arms which were
strained and twisted in a terrible manner, fever which mounted at a
furious speed, and agonising pains in the head.  Many of the victims
were already _in extremis_, several died even while the doctor was
examining them, and in the course of a few hours practically everyone
attacked by the disease had succumbed.  The only ones to recover were a
few children, too young to give any useful information.

It would be useless to trace or describe the excitement which followed,
even though the Press, at the instigation of the Government, was silent
upon the matter.  Help was rushed to Moorcrest, the dead were interred
and the living helped in every way.  The Ministry of Health sent down
its most famous experts to investigate.  One and all admitted that they
were completely baffled.

On May 21st Ancoats was the scene of an appalling outbreak of the
disease.  People in the densely packed areas died like flies.  But there
were some remarkable circumstances which drew the attention of the
trained observers who rushed to the spot to inquire into the phenomenon.

Ancoats had been the scene of the second explosion twelve days before.
It was not long before a health official noticed the coincidence that
the outbreaks at Moorcrest and Ancoats occurred exactly twelve days
after the explosions in each place.

The coincidence was, of course, remarked upon as somewhat suspicious,
but it was not until it was reproduced in the terrible outbreak at
Nottingham that suspicion became a practical certainty.  It was speedily
confirmed by repeated outbreaks in other parts of the country.  In each
case the mysterious malady broke out exactly twelve days after the
appearance of the violet vapour.  In all cases the symptoms were
precisely alike, and the percentage of deaths was appalling.  Neither
remedy nor palliative could be devised, and the best medical brains in
the country confessed themselves baffled.

By this time there was no room for doubt that the terror was the
deliberate work of some human fiend who had won a frightful secret from
Nature's great laboratory.  But who could it be, and what possible
object could he have?

Leading scientific men of all nations poured in to England to help.  For
it was now recognised that civilisation as a whole was menaced; the fate
of England to-day might be the fate of any other nation to-morrow.
France and the United States sent important missions; even Russia and
Germany were represented by famous bacteriologists and health experts.
International jealousies and rivalries appeared to be laid aside, and
even the secret service, most suspicious of rivals, began for once to
co-operate and place at each other's disposal information which might
prove useful in tracking down the author of the mysterious pestilence.

On the day of the meeting of the British Cabinet, two men and a pretty,
dark-haired French girl were keenly discussing the terrible problem in a
small but tastefully furnished flat in the Avenue Kleber, in Paris.

"I know only three people in the world with brains enough to carry the
thing out," said the girl.  "They are Ivan Petroff, the Russian; Paolo
Caetani, the Italian, and Sebastian Gonzalez, the Spaniard.  They are
all three avowed anarchists, and, as we know, they are all chemists and
bacteriologists of supreme ability.  But I must say that there is not a
scrap of evidence to connect either of them with this affair."

The speaker was Yvette Pasquet, and there was no one in whom Regnier,
the astute head of the French Secret Service, placed more implicit
confidence.

"If the doctors could settle whether this poisoning is chemical or
bacteriological it would help us a great deal," said Dick Manton.  "If
it is chemical, I should be disposed to include Barakoff; he knows more
about chemistry than all the others put together.  But in any case,
there is as yet nothing we can even begin to work on."

A fortnight went past.  The death-roll in England had assumed terrible
proportions, and apparently the authorities were as far off as ever from
coming to grips with the mystery.  But a clue came through the heroism
of a London policeman.

One night Constable Jervis was patrolling a beat which led him through
some tumbledown streets in the lowest quarter of Canning Town.  Suddenly
he caught sight of a man rushing from a small empty house.  At once
Jervis started in pursuit of the man, who was running hard away from
him.  As he did so, there came the sound of an explosion, and the house
the man had just left collapsed like a pack of cards.  At the same time
the odour of the dreaded violet vapour completely filled the narrow
street.

The Terror had attacked London, and Jervis knew that to cross that zone
of vapour meant certain death.

He did not hesitate.  Muffling his face with his pocket handkerchief as
he ran, he dashed at full speed after the stranger, whom he could just
discern.  He crossed the zone of death, almost overpowered by the
curious scent of petrol and musk that loaded the still air, and a moment
later was in pursuit, blowing his whistle loudly as he ran.  A moment
later a second policeman, hearing his colleague's whistle, stood at the
end of the road barring the way.  The desperado was trapped.

Snatching out a revolver, the man backed against the wall and opened
fire on his pursuers who were rapidly closing in on him.  But both the
policemen were armed, and both opened fire.  Jervis's second shot killed
the man on the spot.

He proved to be a well-known member of a Russian anarchist group which
had its head-quarters in the slums of Soho.  The gallant Jervis had
faced certain death--as a matter of fact he was among the hundred or so
victims when the epidemic broke out twelve days later--but he had done
his duty in accordance with the splendid traditions of the force to
which he belonged.

The source of the mysterious epidemic was now, to a certain extent,
localised.  It needed no great acumen to guess the motive and origin of
the fiendish plot.  But to discover the master-mind which held the full
solution of the mystery was another matter.

The first step was a general round-up of known members of the Anarchist
Party.  They were arrested by dozens, and very soon practically all who
were known were under lock and key.

To the intense surprise of the police, one and all acknowledged that
they were fully familiar with the scheme.  Many of them had actually
taken part in its execution.  The secret had been well kept!

The explosions, it was learned, were caused by small bombs about the
size of an orange.  These were placed in the selected houses and timed
to explode in a few hours.  Evidently there was some defect in the
mechanism of the one sent to Canning Town, and the man who placed it
there must have seen that it was likely to explode prematurely and
rushed in panic from the house.

But of the source of the bombs one and all of the men professed complete
ignorance.  They were, it was asserted, received by post from different
places on the Continent.  It was evident that the crafty scoundrel at
the head of the terrible organisation took elaborate precautions to
prevent their sources of origin being discovered.

But to have traced the outbreak to Anarchist sources was a step of the
first importance.  Immediately every branch of the secret service of the
western world was concentrated on the problem.

A hint from one of the men captured, who collapsed under the
cross-examination to which the known leaders were subjected, put the
police in possession of one of the bombs.  It had arrived by post the
day before, and the miscreant to whom it was sent was caught before he
had time to make use of it.

It was now possible to prove definitely that the disease caused by the
bombs was chemical in its origin.  Upon analysis the powder with which
the bomb was filled was found to consist of a series of, apparently,
quite harmless chemicals.  A small portion fired by the detonator found
in the bomb gave off dense clouds of the pale-violet vapour, and animals
exposed to it were speedily killed, exhibiting every symptom of the
terrible disease.  Unhappily the secret of the detonator used defied
discovery.  The one found in the bomb had been used in the only
experiment that had been made, and too late it was discovered that no
fulminating material known would explode the apparently harmless powder.

"That seems to narrow it down to Barakoff," said Dick Manton a few days
later when Regnier brought them the news.  "I don't think either of the
others is equal to research work capable of producing such results.  Do
you know where Barakoff is now?" he asked in French.

Regnier shook his head.

"He was in Moscow a year ago," he replied, "and after that we heard of
him in Prague, in Rome, and lastly in Madrid, but he disappeared
suddenly and we have not been able to pick up his tracks again.  He is a
short, powerful, thickset man with a rather hunched back, but nothing
else peculiar about his appearance."

Next day, however, Regnier came to the adventurous trio in great
excitement.

"Barakoff is in England!" he declared.  "We have just had word from
Gaston Meunier who saw him in Brighton a week ago!"

"But how on earth did he get there?" asked Jules.  "You know every one
has been looking for him for months past.  He could not possibly have
got through by any of the ordinary routes."

"I'm as puzzled as you are, monsieur," was Regnier's reply.

"Well, if he is there we'd better go over," said Dick.  "Yvette can go
with me in Mohawk II and Jules by the night boat.  I shall fly the
Mohawk to my old shed in Norfolk; I have kept it on in case of
emergency, and it is quite safe."

An hour later Dick was in close talk with a young Russian named Nicholas
Fedoroff.  He had been an active member of a circle of dangerous
anarchists in Zurich, but had dropped out and was now living in Paris.
By good fortune Dick had saved his baby girl, at imminent risk of his
own life, from being killed by a motor-van in Paris, hence Fedoroff was
impulsively grateful.

"Look here, Nicholas," said Dick bluntly.  "I want you to tell me
anything you can about Barakoff."

They were seated in a small cafe in the Rue Caumartin, which was
Fedoroff's favourite haunt.  The Russian glanced round fearfully.

"Hush!" he said in broken French and in evident horror.  "I--I can't
tell you!  He has agents everywhere.  If I were heard even speaking his
name I should never get home."

The man's agitation was so pronounced that one or two men in the cafe
glanced at him curiously.  Dick saw that the mere mention of Barakoff's
name had thrown the Russian completely off his balance.

"Come to my flat," he said quietly, "you have got to tell me."

They drove in a taxi to Dick's flat, where a stiff dose of brandy pulled
the Russian together.  Yet he still trembled like a leaf.

"How did you know that I knew Barakoff?" he asked.

Instantly Dick was keenly on the alert.  He had no idea that Fedoroff
had been associated with the notorious criminal; his appeal to Fedoroff
had been a chance shot.  Evidently he had stumbled on a matter of
importance.  But he was quick to take advantage of his good luck.

"Never mind how," he said.  "I do know, and that's enough.  You have got
to tell me.  I believe Barakoff is at the bottom of the trouble in
England.  I know he is there, and I want to know where he is and how he
got there."

The Russian's agitation increased.

"You must not ask me; I cannot tell you," he gasped.

"Then a few words from me in a certain quarter--not the police," Dick
suggested.

The Russian collapsed.

"No, no, I will tell you," he moaned.  "He is in England, but I don't
know where.  He flew over."

"Flew over!" echoed Dick in utter amazement.  "Nonsense, he couldn't
have got in that way.  Every aerodrome in England has been watched for
months."

"But he did," the Russian asserted.  "He has his own aeroplane.  It
makes no noise, and it goes straight up and down."

Here was a surprise indeed!  The secret of the helicopter with its
almost unlimited power for evil was also in the hands of one of the most
desperate ruffians in the world!  There was indeed no time to be lost.

Fedoroff could tell Dick little more.  What the secret of Barakoff's
influence over him was Dick could not fathom.  He would say nothing, but
evidently was in deadly fear.

One little item Dick did indeed extract and it was to prove valuable.
Fedoroff knew that Barakoff had associates in Soho.  And that was the
only clue they could gain to his possible whereabouts.

That evening Dick, Yvette, and Jules crossed to England, and with
official introductions from Regnier, Dick lost no time in getting into
communication with Detective Inspector Buckhurst, one of the ablest men
of Scotland Yard's famous "Special Department," a man whose knowledge of
the alien scum which infested London was unrivalled.  To him Dick told
all he knew.

Buckhurst looked grave.

"I know of the man, of course," he said, "but I have never seen him and
I don't think any of my men have.  We have combed Soho out pretty
thoroughly, but no one answering to Barakoff's description has been
seen."

The position was very grave.  If Fedoroff's information was correct--and
Dick saw no reason to doubt it--here was a desperate scoundrel lurking
in England armed with an aeroplane of unknown design and power, and in
possession of a terrible secret which, unless his career was brought to
an end, threatened the entire population of the country.  But where was
he hiding, and, above all, where was his machine?  Could it possibly be
hidden, Dick wondered, in the very heart of London?  The idea was almost
incredible, but Dick knew Barakoff's undoubted genius and his amazing
daring.

A remarkable feature of Yvette's personality was her wonderful influence
over children.  They seemed literally to worship her.  She would get
into conversation with the half-tamed _gamins_ of the streets and in a
few hours they would be her devoted slaves.  She now proceeded to enlist
the ragged battalions of Soho in a fashion that caused Buckhurst much
amusement.

"Find out for me all the hunchbacked men you can," was all the
instructions she gave them.

"But, mademoiselle," said Inspector Buckhurst, "it will be the talk of
Soho, and our man if he is there will slip away."

Yvette was unmoved.

"Just think a minute," she said.  "Who can go about all day and all
night without being suspected?  The children.  Who can go into dens
where your men hardly dare to venture?  The children.  Who know all the
hidden haunts of which your men are utterly ignorant?  The children.
And finally, who are the most secretive people in the world?  Again the
children.  Do not fear, Monsieur Buckhurst, they will not talk except
among themselves, and that will do no harm."

Buckhurst was far from satisfied, but he had gained such a respect for
Yvette that he did not venture to override her.  At the same time, he
told her plainly that he should keep his own men busy.  Yvette only
laughed.

During the next forty-eight hours dozens of hunchbacked men were
reported.  Many of them were people whom not even the police knew.  They
were, of course, mostly harmless, but Buckhurst opened his eyes when one
of them proved to be a notorious forger for whom the police had been
looking for some months, and who had all the time been hidden under
their very noses!  Buckhurst began to feel a growing respect for the
amazing French girl, who had beaten his smartest detectives on their own
ground.  But, unfortunately, none of the hunchbacks was the man they
wanted, and at last they began to suspect that Fedoroff's information
was at fault.

Then came a dramatic surprise.  One of Yvette's small assistants, a
sharp little Polish Jew boy, came to her with a strange story.  He had
been wandering about the night before and had seen a hunchbacked man let
himself out of the side door of a big building half-way between Greek
Street and War dour Street.  The man had walked a considerable distance
in a northerly direction into a part of London the boy did not know at
all, and had entered an unoccupied house, stayed a few minutes, and come
out again.  The lad had shadowed him all the way, and had followed him
homewards, until he again entered the building in Soho.

Dick, Jules, and Yvette turned out at once.  The boy pointed out the
building to them.  It was a tall structure which dominated all the
others in the vicinity.  It was apparently a big shop with storerooms
above.  On the facia over the windows was the name "Marcel Deloitte,
Antique Furniture."  There was nothing to indicate that it differed in
the slightest degree from dozens of other shops and buildings in the
neighbourhood.  Yet Dick felt suspicious.

"We can do nothing till I get the Mohawk handy," said Dick.  "I will
bring her down to-night."

And he paused.

"I wish you would keep out of this, Yvette," he went on wistfully.  "It
is going to be very dangerous, I am convinced."  The French girl was
growing very dear to him, and he shuddered at the idea of her being
mixed up in the coming struggle with a desperado of Barakoff's type.

But Yvette shook her head.

"I'm in this to the finish, Dick," was all she said in her pretty broken
English, and Dick knew he could not move her.  But he was full of fear.

That afternoon another explosion of the pale-violet vapour occurred in
North London not far from Finsbury Park Station.  Dick rushed to the
spot with the boy who had followed the hunchbacked man, and the lad
recognised the place without hesitation.  The house destroyed was, he
was confident, the one the hunchback had entered the night before.

Barakoff was located at last!  But how was he to be captured?  The
problem was not so easy.

It was vital that, if possible, he should be taken alive.  They knew
what would follow the explosion at Finsbury Park, and there was a chance
at least that if Barakoff were captured the secret of the disease, and
possibly the antidote, might be wrung from him.  If they could succeed
in that hundreds of lives would be saved.

Together the three worked out a careful plan for the _coup_ they
intended to bring off next morning.

Very early a dozen street arabs were playing innocently close to the two
entrances of the mysterious building.  They were chosen specimens of
Yvette's band of ragamuffin detectives, and she knew that if Barakoff
tried to escape he would have no chance of eluding their keen eyes.  All
the approaches were blocked by detectives, but Yvette insisted that none
should approach the house itself.  It was essential to the success of
their plan that Barakoff's suspicions should not be aroused.

From the roof of a big building half a mile away, Dick made a careful
examination of what he was now convinced was Barakoff's hiding-place.
But he could see little.  The roof was flat, but it was surrounded by a
parapet practically breast high.  There was obviously plenty of room to
conceal a small aeroplane, but Dick could see nothing.

Dick and Buckhurst together saw the proprietor of the building from
which Dick had made his observations.  He readily consented to Dick's
plan, and towards evening placed a trusty commissionaire at the foot of
the flight of steps leading to the roof with instructions that no one
was to pass on any account whatever.  Soon after dark the Mohawk dropped
silently on to the flat roof.  They were ready now to catch their bird!

In the morning Yvette, under the pretence of wishing to buy some old
furniture, entered the shop.  So far as she could see there was nothing
suspicious.  There was a manager, evidently a Russian, and two
assistants.

Asking for a Jacobean chest which she did not see in the shop, Yvette
was at length invited to the upper floors.  These she found to be full
of furniture.

Climbing the stairs to the third floor, accompanied by the manager,
Yvette found herself in a large room divided in the centre by a wall,
and with a door in the middle.  Opening this door the manager bowed to
her to precede him, and Yvette, quite unsuspectingly, obeyed.  Next
second the door crashed to, and she heard a key turn in the lock.  She
was trapped!

Before she could recover from her astonishment there was a rush of feet
behind her, and she found herself seized in a grip which, as she at once
recognised, it was far beyond her strength to shake off.  She struggled
frantically, but in vain.  She was hopelessly overpowered and swiftly
bound, and laid, gagged and helpless, on a sofa in the corner of the
room.  Then for the first time she caught sight of her captor.  She
recognised him at once.  It was Barakoff himself!  _Worse still, he knew
her_!

The man was mad with rage, his face convulsed and his eyes blazing with
fury.

"So, Mademoiselle Pasquet!  We meet at last!" he snarled, stooping over
her until his face was within a foot of her own and she could feel his
hot breath upon her cheek.  "But it is for the first--and last time!"

Accustomed as she was to danger in many forms, Yvette could not repress
a shudder.  In the power of a ruffian like Barakoff!  She knew, of
course, that at any moment Jules might become suspicious of her long
absence and come in search of her.  But how long would he be and what
might happen in the meantime?

Barakoff set swiftly to work and fixed inside the doors heavy bars
which, as Yvette realised with a sinking heart, would effectually shut
out anyone trying to gain admittance, until either the door was reduced
to splinters or a hole was knocked in the wall.  Then he picked her up
without an effort and carried her into the adjoining room.  This, to
Yvette's intense surprise, was elaborately fitted up as a chemical
laboratory, with all kinds of strange instruments and apparatus.  It was
evident that it had long been used for this purpose.

With an evil sneer Barakoff took from a cupboard what Yvette had no
difficulty in recognising as one of the poison bombs!  This he placed on
a table and attached to it a short length of fuse.  Then he began to
busy himself with what seemed to be preparations for leaving, packing a
few articles of clothing in a small bag and laying it down with a heavy
coat beside it.

"When night comes, I go," he said.  "But you--you will remain.  But I
shall leave you in good company, mademoiselle," and he pointed to the
deadly bomb.  "You will not feel dull.  And after I am gone you will
die--very slowly--of the twisted arms."

For a few minutes the miscreant sat silent, smoking a cigarette and
regarding Yvette with a look of triumph she found even harder to bear
than the consciousness of her terrible danger.

Jules, on watch below, had at length become uneasy.  He entered the shop
and asked one of the assistants if the lady was still there.

"Yes," replied the fellow readily, "she is upstairs with the manager
looking at some furniture."

Jules, his hand on his pistol in his pocket, and feeling strangely
uneasy, started up the stairs.  There was no one in the building.  What
could have become of Yvette and the manager?

On the third floor he noticed the door through which Yvette had gone.
He seized the handle and tried to open it.  But the door was locked and
there was no key.

Not daring to raise an alarm for fear of the consequences to Yvette,
Jules hastened down the stairs, and signalled to one of the Scotland
Yard men.  In a low voice Jules told him what had happened.

"We must be ready to break down that door at once," he said.

With swift efficiency help was summoned, including a couple of men of
the salvage corps, armed with powerful axes which would make short work
of any ordinary door.

While the shop assistants were kept under surveillance, Jules and his
helpers mounted to the third floor.  They tried the door, and knocked.
There was no reply, but inside they heard the hasty scurry of feet.

"Break it down," said Inspector Buckhurst, who had been one of the first
to arrive.

The salvage men sprang forward, and one on each side of the door began a
furious attack with their axes.

Instantly a shot rang out.  Splinters flew in showers, but the door,
heavily barred and plated with iron, for a time defied all their
efforts.  At last it gave way, and headed by Jules the police party
rushed in.

Their first discovery was Yvette, lying unconscious and bleeding
profusely from a wound in the shoulder.  Barakoff had fired at her as he
hurried from the room when the thunderous attack on the door began.  But
in his blind haste his aim had been bad, even at such short range, and
she escaped with comparatively slight injury.

But where was Barakoff?

Rushing out on to the flat roof Jules looked hurriedly round.  To the
southward a queer-looking aeroplane was just vanishing into the thin
mist.  But behind it, going "all out," sped the Mohawk in furious
pursuit.  Dick Manton was taking a hand in the game of which he was a
master!  There could be but one end to that, Jules thought, with a sigh
of relief as he turned to look after Yvette.

She was recovering consciousness and they were just about to carry her
out, when one of the policemen with a loud cry dashed to the table.  He
had caught sight of a thin thread of smoke rising from the fuse of the
bomb!

Luckily he was an old bombing instructor and knew what to do.  A moment
later the fuse was cut and the bomb's detonator removed.  It was
harmless now.  Half a minute later it would have exploded.

Watching keenly from his roof Dick Manton had seen Barakoff's aeroplane
rise swiftly and silently into the air.  He had some slight trouble in
starting the Mohawk, and the Russian was a mile away before the
Englishman had started in pursuit.

Crouched in the driving seat of the Mohawk, Dick kept his eyes glued on
the machine in front.  He soon realised, to his dismay, that the Russian
machine was much the faster and was leaving him behind.  By the time
they had gone ten miles and were out over the open country, he could
only just discern the fugitive as a mere speck in the distance, and he
realised with a sinking heart that a fleck of mist would enable Barakoff
to escape.

Suddenly he discovered that the Russian machine had descended very low.
A moment later it appeared to rise vertically, going up to a great
height.

Instantly Dick followed and to his surprise found himself gaining
rapidly.  Then the Russian seemed to slip ahead again.

Several times this was repeated, and Dick at length divined the reason.
The Russian could not run his elevating and driving propellers
simultaneously.  He travelled in a series of swoops, coming down very
slowly as the machine drove forward, and then being compelled to stop
the driving propellers while he gained the necessary height to continue
his flight.  No doubt this was explained by the fact that the planes
were too small to keep the machine up without the elevating propellers.

Dick saw that he held a big advantage.  The Mohawk, though slightly
slower, could rise and go forward at the same time under the influence
of both propellers.

As they sped over Kent, Dick began to realise with joy that he was
gaining.  Slowly the poison-fiend began to come back to him.

Then came the critical moment.  Five hundred yards ahead and a thousand
feet below, Barakoff, close to the ground, must rise soon to gain the
elevation he required.

That was the moment for which Dick had been waiting.  He called on his
machine for the last ounce of effort he had been holding in reserve.

The Mohawk shot forward.  A few seconds later Dick was directly above
the Russian.  So far as air tactics went he had won; the Russian was
entirely at his mercy.

Then began surely the strangest aerial combat ever witnessed.  To and
fro the machines dodged, Barakoff striving to gain height and succeeding
for a moment only to find his pursuer above him again and bullets
whining round him; Dick striving to force the Russian down to the ground
where he must either land or crash.  For fully half an hour the machines
flitted backwards and forwards around the town of Ashford.  Dick had no
fear of the result; his only risk was whether he could send Barakoff
down before dusk came.  Unless he could do this there was every danger
that the Russian would escape under cover of darkness.

At last the end came.

Dick had forced his antagonist so low that, as a last desperate resort,
Barakoff had to leap upward to clear a big group of elms.  He
miscalculated by a few feet, his machine touched the upper branches and
went smashing to earth.  Three minutes later Dick was standing beside
the body of the death-dealer.

Barakoff's machine was a complete wreck and was blazing furiously.  The
man himself had been flung clear and lay in a crumpled heap, stone dead.

There is little more to tell.

The formula for the powder with which the bomb was charged was found in
Barakoff's laboratory, and with it, in Russian, a prescription which, on
being tested, proved to be a complete cure for the disease.  It was
found just in time to save those who would otherwise have been the
victims of the explosion at Finsbury Park.

It was evident that Barakoff must have maintained his laboratory in Soho
for months.  Obviously the manager of the shop was one of his
accomplices, and apparently he had recognised Yvette and deliberately
thrown her into Barakoff's hands.  Then realising that discovery was
inevitable he had slipped out of the building, probably by a window as
neither of the assistants had noticed him leave.  He was never found.
The assistants themselves proved to be respectable young fellows who had
been employed only a few weeks and who clearly knew nothing of the
nefarious conspiracy.

Nothing but the Mohawk had prevented Barakoff's escape!  And Dick Manton
received later on the official thanks of the British Government for his
daring exploit.

CHAPTER FIVE.

THE MASTER ATOM.

"Oh! la la!  How horribly dull life is!  I do wish something really
startling would happen, Dick!"

The words were spoken in pretty broken English by Yvette Pasquet, who,
charming and _chic_, as usual, was sitting with Jules and Dick Manton.
The adventurous trio were dining _al fresco_ in the leafy garden of the
old-world "Hotel de France" on the river bank at Montigny, that
delightful spot on the outskirts of the great Forest of Fontainebleau, a
spot beloved by all the artists and _litterateurs_ of Paris.

"Something will happen suddenly, no doubt," Dick laughed, glancing at
his beloved.  "It always does!"

"I sincerely hope it will," declared Jules in good English.  "We're
really getting rather rusty.  I met Regnier yesterday out at Pre Catalan
with Madame Sohet, and he hinted to me that some great mystery had
arisen; but he would tell me nothing further."

"Regnier, as head of the Service, is always well informed, and like an
oyster," Yvette remarked with a laugh.  "So I suppose we must wait for
something to happen.  I hate to be idle."

"Yes.  Something will surely happen very shortly," said Dick.  "I have a
curious intuition that we shall very soon be away again on another
mission.  My intuition never fails me."

Dick Manton's words were prophetic, for on that same evening before a
meeting of the Royal Society in London, Professor Rudford, the
world-famed scientist, made an amazing speech in which he said:

"Could we but solve the problem of releasing and controlling the mighty
forces locked up in this piece of chalk, we should have power enough to
drive the biggest liner to New York and back.  We should have at our
disposal energy unlimited.  The daily work of the world would be reduced
to a few minutes' tending of automatic machinery.  And, I may add, the
first nation to solve that problem will have the entire world at its
mercy.  For no nation, or combination of nations, could stand even
against a small people armed with force unlimited and terrible.  And--
gentlemen--_we are on the way to solving that problem_!"

As the words fell slowly and calmly from his lips his hearers felt a
thrill of ungovernable emotion, almost of apprehension.  For they knew
well that he spoke only of what he knew, and the measured phrases
conjured up in their keen brains not only a picture of a world where
labour had been reduced to the vanishing point, but of a world where
evil still strove with good, where the enemies of society still strove
against the established order of things which they hated, where crime in
the hands of the master criminal, armed with force whose potentiality
they could only dream of, would be something transcending in sheer
horror all the past experiences of tortured humanity.

Supposing the great secret _fell into the wrong hands_!

The speech at the Royal Society was a nine days' wonder.

The unthinking Press made merry in the bare idea of a lump of chalk
being a source of power.  Then the transient impression faded as public
attention returned to football and the latest prize-fight.  But behind
the scenes, in a hundred laboratories, students bent unceasingly over
their myriad experiments, striving to wrest from Nature her greatest
secret, the mystery of the mighty energy of the atom.  Since the day
when Madame Curie had discovered that in breaking up, yet seemingly
never growing less, radium was shooting off day and night power which
never seemed to diminish, the minds of the men of science had been
filled with the dream of discovering the secret.

Could they learn to accelerate the process?  Could they induce radium to
deliver in a few moments the power which, expending itself for centuries
untold, never seemed to grow less?  Could they learn to control it, or
would it, when at last the secret was discovered, prove to be a
Frankenstein monster of titanic power, wreaking untold destruction on
the world?

A thin, keen-faced man sat facing the British Prime Minister in his
private room in Downing Street a few days later.  This was Clinton
Scott, one of the smartest men of the British Secret Service, a man of
wide culture and uncanny knowledge of the underworld of international
crime.  His profession was the detection of crime; his hobby science in
any form.

"We have very disturbing news, Scott," said the Prime Minister, "and I
have sent for you because the problem before us is largely of a
scientific nature and I know all about your hobby."

Clinton Scott smiled.

"You are aware, of course, of the latest developments in the search for
some method of releasing and controlling atomic forces," went on the
Prime Minister.  "I do not profess to understand them deeply myself, but
I have a general idea of what is being done and what success would
imply.  Professor Rudford, to whom I applied for information on the
subject, tells me that such a discovery would revolutionise world
conditions.  You will understand of your own knowledge all that it
implies, and that is why I have sent specially for you in this matter."

"I am at the country's service," replied Scott.

"Now information we have received from Norway suggests very strongly
that the problem has been solved," the other said.  "We have no
details--nothing in fact very definite at all.  But it is certain that
some very queer things have been happening.  And from what Professor
Rudford tells me I am assured that we cannot afford to neglect them.
Our ordinary men are useless for this kind of thing.  Men with a
considerable knowledge of scientific subjects are absolutely necessary.
Otherwise matter which, properly understood, would be full of
significance will be passed over as of no account and quite minor and
unessential incidents will be followed up, and there would be serious
waste of time.  And time is valuable."

"I agree that it is," was the terse reply.

"I want you to go to Norway and look into the matter," the Prime
Minister went on.  "Of course I will see that you get all the
information we have, and you can select your own assistants."

Clinton Scott suddenly looked grave.

"Is it known at all?" he asked.  "Who is behind this--I mean who has
made this discovery?  You will appreciate my reason for asking.  If it
is the work of a genuine man of science there would be no immediate
danger, though of course such an invention would upset all ideas of
international relations.  It is literally true, as no doubt Professor
Rudford will have told you, that the nation in exclusive possession of
such a secret could dominate the world.  But there are one or two men in
the world who, with such a secret in their possession, would be a real
peril to civilisation."

"Do you know a man named Lenart Gronvold?" asked the Premier.

Clinton Scott started visibly.

"Do you mean to say he is in it?" he gasped in utter astonishment.

It was the Premier's turn to be surprised.

"Why--who is he?" he asked.  "Professor Rudford had never even heard his
name and laughed when I suggested that he could have had anything to do
with it."

"He won't laugh when he gets some real idea of Gronvold's ability," said
Scott bitterly.  "The man is one of the mysteries of the world of
crime," he went on.  "Exactly who he is we don't know--I mean we know
little about his life.  But we believe he is Norwegian born, though he
has strong Russian characteristics.  We know he studied at Leipzig.
Tutors who knew him well speak with the utmost admiration of his amazing
brain power as a student and the daring of his conceptions.  But for
some reason he never did well in examinations and attracted no attention
whatever outside a very limited circle.  Personally, I believe that for
some strange reason he deliberately elected not to call attention to
himself, for there is not the slightest doubt that he could with ease
have captured every honour the University had to bestow.  After leaving
Leipzig he disappeared for some years.  I don't know how he spent them.
But I do know that he is a chemist of amazing ability.  He has,
moreover, been mixed up with a number of puzzling international crimes,
though we have never been able to bring any of them home to him.  Do you
remember the big bank robbery at Liverpool three years ago?"

The Premier nodded.

"You mean," he said, "when the bank vaults were blown open with dynamite
and half a million in gold stolen?"

"That's the case," said Scott.  "Only it wasn't dynamite, there was no
explosion.  The thick steel and stone walls of the vaulted safe had been
melted through as if they had been butter.  The story of an explosion
was deliberately given out to deceive the thieves.  But the fact is that
some process was used of which we have no knowledge whatever."

And he paused, then went on:

"Now I am pretty sure Gronvold was in that.  I was called in before
anything had been touched.  And in one corner I picked up a scrap of
paper bearing some queer formulae of which I could make nothing.  It had
evidently been dropped by accident.  And it bore Gronvold's name.
Moreover, as I ascertained by a visit to Leipzig, where I saw some of
the old University registers, it was in his handwriting.  But where he
is, how he got into England, how the burglary was effected and how he
got away with such an enormous weight of gold we never could make out.
If he is really in this new discovery we are face to face with a
terrible problem.  The man is absolutely without scruple, and for three
years he has had the use of half a million of money for his experiments.
He may have done anything in that time."

"But how did you know of him?" asked the Premier.

"It's a queer story," replied the other.  "Simmons, one of our men in
Christiansand came across, quite by accident, a drunken Norwegian sailor
who told a strange story of the blowing up of a mountain by a tiny
cartridge placed at the bottom of an old mine shaft.  He actually
mentioned Gronvold's name, and claimed to have been one of his
assistants.  When he became sober he was evidently terribly alarmed at
having talked, and denied the whole story.  The same day he disappeared,
and Simmons has been unable to trace him."

He went on after a pause:

"Now the blowing up of a mountain is a fact.  A hill nearly a thousand
feet high in a wild lonely district north-east of Tonstad has absolutely
disappeared--levelled out.  To have done the work by ordinary means
would have meant years of labour and would have cost a fortune.  There
can be no doubt that some entirely new force has been employed.
Officially the occurrence is attributed to a landslide; actually it is
and can be nothing of the kind.  Now this, coupled with what the
Norwegian sailor said, suggests that we ought to look into the matter.
Whether the Norwegian Government knows anything about it I do not know,
and the matter would be of such importance from the international point
of view that we cannot make direct inquiries."

"Will you take it in hand?" asked the Premier.  "Whom will you get to
help you?  I am afraid the ordinary men would be of very little use."

"I think I will run over to Paris and see Regnier," replied Scott.  "He
has a fellow named Manton who will certainly be useful.  He was in our
flying corps and was invalided out owing to wounds.  He has done some
wonderful work and has an entirely new type of aeroplane which he
invented and which, by the way, our people would have nothing to do
with.  Regnier swears by him.  He works always with a French girl named
Yvette Pasquet, who did some splendid intelligence work during the war,
and her brother Jules.  They will have nothing to do with anyone else
when they are on a case, and they have had some amazing results."

Crossing to Paris by the afternoon air express Scott the same evening
was warmly greeted by Regnier.  He rapidly explained his visit.  Regnier
looked grave.

"I have heard of the man," he said, "but have never seen him, I don't
think in a case like this you can do better than Manton.  He is very
well up in all these scientific things; they seem to be a perfect craze
with him."

An hour later, Regnier, Scott, Dick Manton, Yvette, and Jules were
closely discussing the problem in Manton's rooms.

"We have got to find that sailor," was Dick's verdict, "and luck is
going to have a good deal to do with it.  I suppose Simmons is on the
look out for him?"

"Yes," replied Scott, "I wired him at once."

"Do you think Gronvold and the sailor have quarrelled?" put in Yvette.

"I think not," was Scott's reply.  "If they had there seems no reason
for the man's alarm.  I think he calculated on going back to him.  That
was Simmons' view, too."

Dick, who had been carefully studying a map, looked up.

"Just look here," he said, "you could hide an army in this place."

The map was in contour and gave a vivid impression of the wild and
desolate country, a broken mass of hills and lakes, stretching north and
east from Tonstad.

"Suppose Gronvold is there," said Dick, "he could hide anything he
wanted to.  I don't think he would have travelled far from its base to
blow up the hill--that was probably experimental.  My idea is that he
has established his laboratory somewhere in the hills about there.
There is no population and little or no traffic through the district.
He must send to one of the towns for supplies, and Christiansand is the
most likely.  I should guess that the sailor had come there for that
purpose and may come again."

"He did not leave the town by boat," declared Scott.  "Simmons made the
most careful inquiries on all the boats in the harbour and no one of his
description was seen."

Three tourists a week later were lodged in a comfortable hotel in the
Dronningens Gade, one of the principal streets in the busy port of
Christiansand.  They were Yvette, Jules, and Scott.  Dick had flown the
Mohawk direct to the wild district north-east of Tonstad, and with the
help of a light tent had pitched a camp in a little wood a couple of
miles from the southern edge of the blown-up hill.  He had taken pains
in the selection of a suitable place and his camp and the Mohawk were so
admirably hidden that they were safe from discovery, unless some one
actually walked right up to them, a contingency which in that roadless,
unpopulated country was extremely unlikely.  But though hidden himself
he commanded a wide view.

For two days Dick devoted himself to a thorough examination of the
surrounding country, quartering it thoroughly either on foot or in the
Mohawk.  He could however see nothing in the least suspicious.

Then came a surprise.

His only method of receiving news from the others was to "listen in" on
the wireless telegraph set with which the Mohawk was fitted for messages
which, directed to an address in England, were handed to the
Christiansand radio station for dispatch, but were really intended for
him.  These messages were handed in at eight o'clock precisely and Dick
usually got them within half an hour.

On the third day of his watch came the message:

  "Sailor located.  Travelling north with pack mules.  We follow.
  Osterluis road."

The man, as he was to learn later, had been spotted by Yvette in
Christiansand.  She had seen him leave a small cafe much frequented by
sailors, and had been struck by his likeness to the description given by
Simmons.  She had followed him for some time while he made a variety of
purchases at numerous shops, and had been struck by the fact that a mere
sailor should evidently have such a large sum of money at his disposal.
Luckily she had encountered Simmons, who at once recognised the man and
had promptly disappeared to avoid arousing his suspicions.

Yvette was able to learn that all the man's purchases were being
delivered to a small inn on the outskirts of the town, and a few
inquiries showed that he had four mules stationed there.

The matter began now to clear up.  They were sure of the man; at least
he could not leave without his mules and stores.  Jules and Scott took
up the watch at the inn, while Yvette shadowed the suspect.  It was
thought best that Simmons should not appear.  It soon became evident
that the man had no associates in Christiansand.  All he did was to
visit shops, paying cash for all his purchases and having them sent to
the inn where his mules were stabled.

The next day, with his mules heavily loaded, he set out from
Christiansand, taking the road to Trygstand and Ostersluis.

Yvette, Jules, and Scott decided to follow him on foot.  To have taken
horses would have told him he was being followed as soon as he left the
road, as they were pretty sure he would, sooner or later.  Luckily all
three were splendid walkers and felt they would have no trouble in
keeping up with the heavily-laden mules.  Cramming a few necessities
into rucksacks they were soon on the track of their quarry.

Man and mules made steady progress.  They were soon through Trygstand
and, shortly after, caught sight of the Mohawk high above them and
evidently following the road on the watch for them.

With a handkerchief tied to a stick Yvette swiftly signalled to Dick the
brief facts, and the Mohawk passed on towards Christiansand.  When the
sailor and the mules were hidden in a dip in the road Dick landed, and
all four held a brief consultation as to their future plans.

As a result Scott put on his best speed and soon passed the sailor who
had stopped for a rest.  The man was now between two parties on the
ground and under observation from Dick from the air.  He certainly could
not escape.

A few miles beyond Trygstand he suddenly left the high road, and turned
westward and north across the open country.  Evidently he was not bound
for Ostersluis.  But where could he be going?  For miles there was not
even a house in the deserted track of country into which he had plunged.

But it was evident he knew his bearings thoroughly.  Hour after hour he
jogged along, and soon the pursuers realised that they had been wise not
to bring horses.  No horse could have crossed the country over which the
sure-footed mules went swiftly without a stagger.

At nightfall the man camped.  Apparently he paid no attention to the
passing of the aeroplane, for he barely glanced at it.  Building a small
fire under the shelter of a rock, the three pursuers spent a comfortless
night.  Dick had flown to his camp, intending to pick the party up again
at dawn.

Early next morning the man was afoot and continued his journey.  He was
now in the wild country well to the west of Ostersluis, and travelling
due north.  Yvette, Jules, and Scott were a mile behind, following with
the utmost care not to reveal their presence and so rouse the man's
suspicions.

They had gone but a few miles when the man paused on the flat top of a
high hill, which on the side away from them sloped steeply into a deep
gorge at the foot of which ran a small stream.  They watched him
narrowly.

With great care he got the four mules together, standing side by side.
He himself took up a position directly in front of them and almost
touching the animals' heads.

A moment later man and mules sank together, apparently into the earth
and disappeared!

They could hardly believe their eyes!  Surely the man must have gone
down the reverse slope of the hill.  But they were confident that he had
not moved.

They hurried to the spot.  Not a sign of any living thing was to be
seen!  The mystery was profound.

While they stood gazing at one another in speechless amazement, the
Mohawk, which they had not perceived above them, dropped vertically
downwards and landed a few yards away.  Dick sprang out.

"Did you see?" he gasped.  "The man and mules went down into some sort
of pit.  But where was it?"

The flat top of the hill was broken into a series of narrow cracks;
apparently the rock of which it was composed was of volcanic origin.
They examined it closely, but they could discover nothing which offered
a solution of the mystery.

Dick described closely what he had seen from the sky.  It agreed with
what the others had observed.  The man had got the mules together, and
all had sunk slowly downward.  Dick had seen the black mouth of the pit
for a few moments and a blaze of light.  Then the pit had disappeared,
and the ground resumed its normal appearance.

"We shall have to camp here to-night," said Dick.  "We must get to the
bottom of this.  We shall have to take turns to watch.  In the meantime
we had better have a look round."

Having closely examined the top of the hill, they turned to the deep
gorge and descended to the bottom.  The stream, they found, issued from
the hill itself, flowing out from a low tunnel high enough to admit the
passage of a man.  From it also issued a cloud of mist which spread over
the bottom of the little valley in a thick blanket which completely
concealed the surface of the ground from anyone at the top of the hill.

But still more remarkable was that the bed of the little stream was
deeply covered with what appeared to be recently melted lava.  In many
places it was still hot, and the water, they found, was nearly boiling.
The first traces of this were found at the mouth of the tunnel from
which the stream emerged, and for hundreds of yards the molten rock
could be traced, as though it had poured from the tunnel and flowed down
the bed of the brook.

Wood and water were available in abundance, and soon they had pitched
their camp, near enough to the top of the mysterious hill to enable them
to watch it closely and yet well concealed so that if the man reappeared
they would have no difficulty in escaping observation.

The first watch fell to Yvette, and with a revolver ready for instant
use, she prepared to spend a couple of lonely hours on the edge of the
hill.  The camp was but a quarter of a mile away so that a shot would
bring her speedy help at any time.

A brilliant moon lit up the country for miles.

There was no trace of any living thing.  Everything was still and
silent.

Yvette had been on watch about an hour when she became aware that the
air was full of a dull murmur of sound.  She listened intently.  There
was no mistake about it.  A dull throbbing noise was distinctly
discernible.

She walked round the flat top of the hill, looking keenly in every
direction and trying to locate the position from which the mysterious
sound was coming.  But it was in vain.

Glancing into the gorge, she saw a strange and terrible phenomenon.  The
course of the little brook was traced in a dull fiery glow.  Clouds of
steam were rising thickly into the night air; she could plainly hear the
sharp hiss of water on something hot.

She ran swiftly down the hill.  At the bottom she paused on the edge of
the stream.  The water had disappeared and in its place ran a river of
molten rock!  Through her boots she felt the heat of the ground.

Returning to the top of the hill she waited for Dick, who was now almost
due to relieve her.  In a few moments he appeared and listened in
amazement as she gasped out her story.

The dull, throbbing noise was still audible.

"Machinery," said Dick laconically, "but where?"

Suddenly he flung himself on his face, and pressed his ear close to the
ground.

"Listen," he said.

Yvette followed his example.  There could be no mistake; the mysterious
sound was coming from the ground beneath their feet!  The earth was full
of muffled thunder.

Dick took from his pocket a hammer and struck a sharp blow on the flat
rock beneath their feet.  It rang hollow!  Unmistakably they were
standing on the roof of a cavern.

Walking to the camp they roused the others and told them what they had
seen and heard.

"We have got to catch that sailor if we wait here a month," said Scott.
"He must come out again some time.  But how about food?"

"We have enough tinned stuff in the Mohawk for a week," said Dick, "so
we shall be all right for a few days.  In the meantime we must watch the
place closely."

Next day passed without incident until evening was drawing on.  Then
Yvette, who was watching the top of the hill while the others rested, at
six o'clock gave a low whistle.  She was lying on the ground keeping
observation between a couple of rocks which hid her completely.  In a
moment the others had crawled to her side.

"Look!" she said.

On the top of the hill, three hundred yards away, stood the sailor and
the four mules, clearly silhouetted against the evening glow.  He had
appeared suddenly, Yvette told them, just on the spot where he had
disappeared on the previous day.

"We must get him," said Dick.

The man with the mules started to return along the way he had come.
They saw at once that the path he was taking would bring him close to
them.

With the mules unloaded the man evidently had no intention of walking.
He mounted one of the animals and rode towards them at a fast trot.

He was within twenty yards when Dick aimed his revolver and fired.  The
mule the man was riding bolted, throwing its rider heavily.  Before he
could recover himself he was bound and helpless.  The other three mules
stampeded wildly and were soon out of sight.

Carried to the camp the man soon recovered.  But he resolutely refused
to say a word.

"Well," said Dick.  "We must try to get into the cave.  Perhaps the
tunnel out of which the brook runs will lead us to it."

They were soon at the mouth of the strange tunnel.  There was no sign of
the molten matter of the previous night.  The stream, thick with mud,
flowed sluggishly, but the water was cool, and the ground, which the
night before had been too hot to walk upon, was now not more than
uncomfortably warm.

With Dick leading, Scott and Yvette next in order, and Jules bringing up
the rear they entered the mouth of the tunnel.  There was, they found,
just room for them to pass, stooping low and walking knee deep in the
little stream.  They were, of course, in total darkness, for Dick was
afraid to show a light for fear of betraying their presence.

For a hundred yards Dick groped his way onward.  Then his outstretched
hands struck something soft.  It was a kind of curtain hung across the
stream, thick and heavy.

Cautiously he slightly raised one corner and peered through.  The sight
that struck his eyes filled them with amazement.

They were at the entrance to an enormous chamber, a hundred and fifty
yards across, dimly lighted by a single big electric lamp, the only one
alight out of dozens which hung from the roof.  The floor sloped steeply
upwards at the far end where they could make out a kind of platform,
reaching nearly to the roof and with steps leading downward into the
great hall.  All round the side were a series of openings, apparently
small chambers cut into the solid rock.  From one of these the stream
they had followed seemed to issue, crossing the floor of the great cave
in a narrow deep channel.

But what fascinated Dick's attention was a great table, apparently of
iron, which occupied the centre of the cave.  It was heavily constructed
and seemed to be based on massive legs which went down into the rock.
Upon it stood a strange machine unlike anything he had ever seen before
and of the use of which he could not form the smallest idea.  Surmounted
by two huge governor balls, it was a complicated mass of polished
wheels, of some metal which Dick could not identify, and which gleamed
with a strange radiance in the light of the huge electric lamp overhead.
From the machine a bewildering mass of wires led to a series of points
at the face of the rock.

So much Dick could make out in the dim light.  He was keenly anxious to
learn more.  But how was it to be done?  No sign of any human being was
to be seen, but he could not imagine that what lay before their eyes was
the work of the solitary sailor who now lay bound in their camp.

At any rate they could not remain where they were.  Dick decided to try
to gain entrance to one of the wall chambers where they could shelter
with a better chance of seeing what would happen in this underground
home of mystery.  But which should they choose?

Some of the chambers were half-way to the roof and were reached by steps
cut in the solid rock.  Dick decided on one of these not far from where
they were standing.  They crept cautiously from their hiding-place and
stole along to the bottom of the cave.  A moment later they were at the
foot of the steps.  These they hastily climbed, and soon found
themselves in a fair-sized cave, fifteen or sixteen feet above the floor
of the main cavern and commanding a good view of the entire area.  It
was dry and warm and formed an ideal post of observation, provided their
presence remained undiscovered.

Suddenly a blaze of light struck their eyes.  Some one had turned on the
whole of the electric lamps which hung in clusters from the roof.

Peering cautiously out they saw, to their amazement, half a dozen men
issue from different chambers near the floor of the cave.  All wore big
round spectacles of deep blue glass and were clothed in close-fitting
garments of rubber, with heavy gauntletted gloves of the same material.
Apparently they could not see well, for the spectacles must have been
almost impervious to ordinary light.

One of the men, fixing his spectacles on more firmly and, drawing his
rubber overall more closely around him, approached the strange machine
which stood on the table.  The others proceeded to the points at which
the wires from the machine reached the side of the cave.  Here they took
up some kind of tool which looked like a gigantic blowpipe and stood
ready as if awaiting a signal.

A low whistle sounded from the man at the table, as he grasped a small
wheel and gave it a quick turn.

An instant later an appalling blaze of light burst from the strange
machine, and the cave was filled with a roar of sound, a terrible deep
drone of such frightful intensity that the hidden watchers shuddered as
if with actual physical agony.  Dick felt the sweat start suddenly from
his forehead and pour down his face.  Anxiously he glanced towards
Yvette.  She lay with her face buried in her arms, her body trembling
convulsively.  Scott and Jules, their faces white as chalk, were gazing
at the unearthly light which streamed from the whirling machine, shading
their eyes with their hands to shelter them from its blinding radiance.
They could not look at it for more than a few seconds; it was like
trying to gaze at the sun at midday.

Taking a letter from his pocket, Dick bored a tiny hole in it with his
scarf pin.  Through this hole he found he could see in comparative
comfort.  He signed to the others to do the same, and soon all four--for
Yvette quickly recovered her self-possession--were eagerly watching the
strange scene before them.  Speech, in the deafening noise by which they
were surrounded, was, of course, out of the question.

The man at the great table in the centre of the cavern evidently had a
task of great difficulty to control the movements of the strange
machine, which he seemed to do by means of a large wheel something like
the steering wheel of a steamer.  Long streamers of flame shot from it
in all directions, and as its mass of wheels revolved at terrific speed
it shook and trembled as if it would actually leap from the table.

In the meantime the men at the rock face were hard at work with big
blowpipes, from the muzzles of which shot streams of fire of such
intensity that the solid rock seemed to melt away like butter.  The
molten matter was led by ducts in the ground through a grid of some
metal, evidently highly refractory to heat, for it appeared to do no
more than glow white-hot even in the terrific temperature of the melted
rock.  After passing through this grid the molten matter was led to the
bed of the stream, from which the water had in some manner been cut off,
and flowed out the way Dick and his companions had entered.

What was the object of the work?

Dick could not guess, but every now and again one of the men would walk
to the grid and with a long implement shaped like a hoe would scrape off
something adhering to the bars, which he deposited in a big tank of
water.  Dick determined that, sooner or later, he would obtain a
specimen.

But in the meantime their position was decidedly precarious.  If they
were observed there was no possible way of escape, for the tunnel by
which they had entered was barred by the stream of molten matter.  They
could only lie still and hope that no one would enter the gallery in
which they lay concealed.

After two hours of work, the man at the table stopped the machine, and
all the men straightened out for a rest.  Evidently they were very much
exhausted.  The lights were extinguished, except for the single one
which was burning when they entered, and the men returned to their
quarters, evidently almost falling with weariness.  Dick came to the
conclusion that they could only carry on the work on which they were
engaged for a short time and that after that sleep and rest were
imperative.  The flow of molten metal had stopped and the water was
again allowed to flow along its ordinary channel, from whence it sent up
huge clouds of dense steam.

This gave Dick his chance.

Sending the others to the mouth of the exit, he cautiously crept towards
the tank in which were deposited the scrapings from the grid which
filtered the molten rock.  He reached it safely, and plunging in his arm
up to the shoulder, abstracted a couple of handfuls of what seemed like
heavy shot.  These he placed at once in his pocket.

He was about to return to the others when his attention was caught by
the queer platform at the one end of the cave.  Looking at this
carefully he found that it was really a huge lift, and at once the
mysterious disappearance of the sailor and the mules was explained.  It
was evident that the top of the lift was really the thin covering of
rock which had sounded hollow when tapped and that this had been so cut
that when the lift forced it into position only traces of ragged
crevices were left on the surface.  Dick could not but admire the
ingenuity with which this approach to the subterranean retreat had been
devised.

Presently he heard a heavy knocking above his head and, guessing the
cause, shrank back for shelter into the mouth of a small cave adjoining.
A moment later a man emerged from one of the other chambers and
approached the lift.  Dick was curious to see how it worked.  There was,
as he could see, a small electric motor fitted to it, but where could
the necessary power come from?

The new-comer carried in his hand a tiny machine which was in every
respect a duplicate in miniature of the big one on the central table.
But it was so small that the man carried it easily in one hand.  From it
ran a pair of electric cables which the man proceeded to connect with
the terminals of the motor.

Placing the machine on the ground he gave the wheel a sharp turn.
Immediately the tiny machine began to revolve, throwing out flashes and
flames exactly like the larger one but on a miniature scale.

Clearly, however, there was considerable power in it, for the lift at
once commenced to descend.  On it stood a man whom Dick instantly
recognised as Gronvold.  And he was accompanied by the sailor whom Dick
had left safely tied up in their camp.  Evidently Gronvold had found and
released him.

Their position was now indeed one of terrible gravity.

As soon as the lift reached the bottom the two men stepped off and the
lift reascended, moving upward with an ease which showed the tremendous
power developed by the tiny machine.  Here, indeed, was something of
which Dick had had no previous experience.

The three men crossed the cave to the shelter occupied by the man who
worked the big machine, who was evidently the captain, and Dick knew
there was no time to be lost.

Directly the men entered the shelter, Dick dashed across the cave to
join the others, snatching out his revolver as he ran.

He had nearly reached them, when a whistle blew and instantly half a
dozen men rushed from different caves.  They were discovered!

"Take care of Yvette, Jules!"  Dick yelled as, with Scott at his side,
he faced round to the men who were rushing at them from three sides.

Instantly Yvette and Jules plunged into the tunnel.  Dick and Scott
backed after them with drawn revolvers threatening the men in the cave.

For a moment the leaders hesitated; apparently they were not aimed.
Then Gronvold rushed to the front, followed by the captain, both
carrying curious weapons which looked like heavy pistols.

All four men fired simultaneously.  Dick saw the captain drop, evidently
shot dead, and heard a bullet whiz past him and strike the rock behind.
A burst of flame singed his hair, and he felt the hot breath of it on
his face.

Then Gronvold fired at Scott.  The effect as the bullet struck him was
strange and awful.  His body actually disappeared in a mass of flame
under the impact of some projectile of unimaginable power and energy.
At the same instant Dick slipped on a projecting bit of rock and fell
heavily on his head.  As he lost consciousness he heard the crack of a
revolver behind him.  Yvette and Jules, hearing the shots, had returned
in the nick of time.  Jules snatched up Dick and carried him down the
tunnel, while Yvette very coolly shot down Gronvold just as he was
reloading his terrible weapon.

When Dick recovered his senses he found himself lying on the ground at
the entrance to the tunnel, his head pillowed on Yvette's arm as she
tried to pour some brandy between his lips.  He could feel the sobs
which shook her, and even felt a tear on his face.  Jules stood on guard
at the entrance to the tunnel, his revolver ready for instant action in
case of pursuit.

As Dick opened his eyes, Yvette gave a gasp of relief.

"Oh, dearest, I thought you were dead!" she sobbed and burst into tears.
A moment later she turned away blushing scarlet.  She had betrayed her
secret at last.  And even in his confused state Dick felt a thrill of
triumphant joy.

His head spinning he staggered to his feet.  But he would have fallen if
Yvette had not caught him.

"Sit down, Dick," she said peremptorily.  "Jules can look after this
place."

Dick obeyed, perforce; he was so sick and giddy that he could have done
nothing even if the expected attack had come.

But it never came.  Suddenly as they stood there, tense and waiting, a
terrific convulsion shook the earth.  With a terrible roar the great
cavern collapsed and a vast burst of smoke and flame vomited to the sky,
and a deep crater was left by the subsidence.  Sick and dizzy, with
showers of stones falling all around them, they stood aghast while
explosion after explosion rent the air, rendering the crater deeper.  It
was some minutes before quiet reigned again and, white and shaken, after
their nerve-racking experience, they were able to collect their shaken
faculties and make an examination of the scene.

The hill beneath which the cavern was located had practically
disappeared; in its place was left nothing but a heap of torn and
tumbled earth and rock.  Its dreadful secret was safe, for the cave and
its contents, and the men who had wielded such titanic forces, were
buried deep under tens of thousands of tons of debris.

Perhaps it was as well, Dick thought.  There are some forms of knowledge
which mortals ought not to possess; there are some powers which they are
not fit to handle.

Whatever secret Gronvold had discovered, it rested with him for ever on
the very scene of his ill-omened labours.  What had gone wrong in the
depths of the cavern they could not even imagine, but it was evident
that the mysterious force which Gronvold had called into existence,
whatever it was, had destroyed him and his companions.  And it was
almost by a miracle that Dick, Yvette, and Jules had escaped.

Slowly and painfully they made their way back to their camp, and for the
first time Dick became conscious of the great weight of the double
handful of shot which he had taken from the tank.  He drew some of it
out and examined it by the light of the fire.  As he did so he gave a
cry of surprise.  For the "shot" was nothing more or less than tiny
nuggets of virgin gold.

Here was an addition to the mystery.  As Dick knew perfectly well, there
was not an atom of gold-bearing rock within hundreds of miles of where
they stood.

It was evident that one of the secrets of Gronvold's invention was that
it gave him the power of actually bringing about the transmutation of
substances.  There was some element in the rock which was susceptible of
being changed into gold by a process at which they could not even guess.
But if this were so, Gronvold had indeed, as they suspected, been able
to solve the problem of loosing the incredible force contained in the
atom.  His discovery was, as Dick at once realised, on the lines of the
latest development of scientific thought.

Dick was to see the problem solved in later years by more reputable
investigators.

But he could never forget his strange encounter with the wonderful but
misguided genius whose career had been so terribly brought to an end by
the dread power he had himself evoked.

CHAPTER SIX.

THE HORROR OF LOCKIE.

Many readers will recall the tragedy of Renstoke Castle and the terrible
death of young Lord Renstoke.  The case aroused much sensation at the
time.  It would have aroused far more had the real facts been allowed to
transpire.

They were known, however, to only a few people, and, for reasons which
were at the time sufficient, they were kept secret.  I am now able to
lift the veil which shrouded one of the most perplexing mysteries which
has ever puzzled the scientific world.  Even now, the story is not
complete; the great secret died with the amazing but perverted genius
who discovered it.

Lord Renstoke, a young man only thirty, was one of those favoured
individuals on whom Fortune seemed to have showered all her gifts.  Born
and brought up in Canada, he was connected only very remotely with the
ancient family of Renstoke, and no one ever dreamed that he could by any
possibility succeed to the title, which carried with it Renstoke Castle
and a rent-roll of something like a hundred thousand pounds a year.

James Mitchell, as Lord Renstoke was before he succeeded to the title,
had left a lumber camp in Upper Canada when the call of the Great War
brought Britishers from all the wild places of the world to join the
colours.  He served as a private in one of the Canadian Regiments,
rapidly winning his way upward, and finally being awarded the Victoria
Cross for a piece of dare-devil folly--so his comrades declared--that
had led to the capture of an important German position and had helped
very materially to bring about one of the most brilliant of the many
successes scored by the Canadians in the closing stages of the fighting.

That episode seemed to mark the turning-point in the fortunes of James
Mitchell.  From then onward it seemed as though Fate had no gifts that
were too good to be showered upon him.  It was only a few weeks later
that the obscure Canadian private was summoned to headquarters to
receive the astounding intelligence that through a series of deaths that
in fiction would have been deemed fantastic, he was a peer of the United
Kingdom with a vast fortune at his disposal.

Then James Mitchell, Baron Renstoke, went back to his trenches and the
comrades he had learned to love to finish the work on hand.

It was during the latter half of the war that James Mitchell found
himself swept by chance into the strange web of mystery and adventure
that surrounded the doings of Yvette Pasquet and Dick Manton.  He had
been detailed, quite privately and "unofficially," to help Yvette in one
of her achievements, and the clever French girl had been quick to
recognise in him an assistant of more than ordinary ability.  Yvette was
one of those rare people who never forget, and so there came about a
gradual friendship which included Dick Manton and Jules Pasquet.  Yvette
rejoiced unfeignedly when, after the Armistice, she learned of
Mitchell's good fortune.  The friendship continued and ripened, and
Yvette, Jules, and Dick Manton were staying at Renstoke Castle when a
terrible stroke of malign fate cut short a career of brilliant promise
and brought an ancient lineage to an end.

Renstoke Castle was a wonderful old house in Argyllshire, and James
Mitchell, now Lord Renstoke, was surely one of the favoured of the gods!
Over six feet in height, strikingly handsome and of superb physique,
wealthy and with great charm of manner, there seemed to be nothing to
which he could not aspire.  Despite the surroundings of his early years
he had been well educated for his father, though only a Canadian farmer,
had been a man of considerable culture and learning, and had seen that
his son, who inherited his own intellectual gifts, had been well taught.
Only the spirit of adventure had led him at twenty-one into the wild
places of the world, where he saw existence from many angles, and in a
rough outdoor life had brought to perfection physical powers which had
been remarkable even in boyhood.

He was now the last of the Renstokes.  But he was still young.  No one
dreamed but that he would marry and that the ancient line would be
continued.

Then the blow fell!

Through the late summer a series of mysterious attacks had been made on
live stock throughout the western portion of Argyllshire.  Sheep, and
even deer, had been attacked, evidently by some unusually powerful
animal.

Sheep worrying, of course, is not an uncommon vice among dogs, and when
the outbreak first started little was thought of the matter.  The local
farmers and shepherds merely began to watch their dogs more closely than
usual.  But the outbreaks continued, more and more sheep were killed,
and at length the losses became so heavy that drastic steps were taken.

For thirty miles around, not a dog was permitted off the chain after
dusk.  Bands of men armed with guns, with instructions to shoot any dog
on sight, patrolled the country-side by day and night.  It was all in
vain.  Sheep continued to perish under the teeth of the mysterious
prowler, and even the smaller deer, in spite of their speed, began to
fall victims.

The farmers were at their wits' ends when the mystery was suddenly
lifted into the region of unadulterated horror.

Alan MacPherson, a young gamekeeper, had been one of a number of men
who, stretched out into a line a couple of miles long, had set out at
nightfall to search a lonely piece of moorland in which it was thought
the strange animal might be hiding.  The line of men had gone forward on
a prearranged plan for five or six miles and then "pivoted" on the right
hand man, swung round and marched homeward, concentrating finally at a
big farm known as Kelsie, where the losses had been very serious.

The men, of course, knew the country thoroughly, and similar manoeuvres
had been many times repeated without mishap.  Always the last man of the
line had turned up within a few minutes of the prearranged time.

On this occasion MacPherson was on the extreme left wheel and, having
farthest to go, should have been the last man home.  No one was uneasy
when it was found he was a few minutes late; he was armed and knew the
country like the palm of his hand.

But when the minutes slipped by without news his companions began to be
anxious.  Three hours passed, and, at length, a search party was hastily
formed.

Two hours later MacPherson's body was found lying terribly mangled
beside a big rock on the slope of a small tor.  His gun, still loaded,
was only three feet away.  Beside the body lay a filled pipe and a box
of matches.  Evidently the man had laid down his gun to light his pipe
and had been suddenly attacked and killed before he could raise a hand
to defend himself.

A few minutes later, Lord Renstoke, Yvette, Dick Manton, and Jules were
on the scene.  Though all were familiar with the ghastly sights of war,
they found themselves in the presence of a horror which overbore all
their previous experiences.

Renstoke, whose experience abroad had made him familiar with many wild
animals quite unknown to the others, examined the body carefully.  At
length he rose from his knees with a horrified expression in his eyes,
and gave brief orders for the removal of the body to the unfortunate
man's home to await the inquest.

But it was not until they had returned to the Castle that he spoke of
what he had seen.  And his first words gave his comrades a terrible
shock.

"No dog did that!" he said quietly, but in a tone of intense conviction.

"Whatever do you mean, Renstoke?" asked Dick quickly.  "What else could
have done it?  There are no lions or tigers about here, you know."

"Are you sure?" replied Renstoke.  "I think we shall have to see
Erckmann about this."  Boris Erckmann, he went on to explain, was a
famous zoologist who lived in a big lonely house on the Renstoke estate
some ten miles away.  He had spent many years in wandering explorations
in tropical countries and was known in the inner circles of science as a
man of brilliant attainments.  He did not advertise himself, however,
living the life of a recluse, and to the general public his name meant
nothing.  Among his Highland neighbours, a dour people who concerned
themselves very little with the affairs of other folk, little notice was
taken of him.  He lived at Lockie, a big house surmounted by a high wall
and perched on a gaunt hill-side overlooking a lonely glen.  Among his
neighbours, who guessed nothing of his wonderful abilities, Erckmann
passed for a harmless scientist and was affable and good-natured to
those he chanced to meet during his incessant pilgrimages over the wide
moorland which stretched for many miles around Lockie.

"Erckmann is said to have a lot of wild animals at Lockie," Renstoke
went on to explain, "and it is possible that one of them may have broken
loose.  I am perfectly certain MacPherson was not killed by a dog."

"But what makes you so certain?"  Dick questioned.  "So far as I could
see any big dog could have done it."

"Did you ever see a dog with hands, Dick?" asked Renstoke quietly.

His hearers started simultaneously with a gasp of horror.

"Whatever do you mean?" they asked.

"Just this," Lord Renstoke replied.  "He was not killed by a dog at all.
As you saw, the front of his throat was badly torn.  But on the back of
his neck were two distinct bruises, one on each side and nearly meeting,
which suggested the mark of two thumbs, as if he had been seized from
behind by two hands which clasped his neck.  Now, no dog could have done
that.  Moreover no dog could have killed him so quickly that he never
had a chance either to fight for his life or to call for help.
Remember, he was an extremely powerful man and his nearest neighbour in
the line was scarcely more than a hundred yards away.  He was killed so
suddenly and so swiftly that he had no time even to shout.  I have seen
many men who had been killed by wolves, bears, and cougars, but never
one who had not made a fight for his life."

"But what could it have been?" asked Yvette in a horrified whisper.

"There is only one animal in the world that could have done it," replied
Renstoke, "and that is a gorilla.  You know the strength of the gorilla
compared with that of a man is enormous.  It has enormously powerful
hands and teeth.  A man seized unawares, as MacPherson must have been,
would be dead in a few seconds; he wouldn't have the smallest chance
either to defend himself or to shout.  And I happen to know, though it
is not generally known, that Erckmann actually has a gorilla at Lockie.
I am going over to see him after the inquest and I mean to see the
gorilla as well.  Erckmann is a tenant of mine, though, as it happens, I
have never seen him.

"But there is one thing that puzzles me," Renstoke went on after a
pause.  "The sheep-killing has been going on for several months, and I
don't see where such an animal as a gorilla, assuming that it has been
at large for so long, can have been hidden without being seen.  But, of
course, the country is very wild and there are some big woods that may
have screened it during the daytime."

"What are you going to say at the inquest?"  Dick asked abruptly.

"Nothing at all until I know a lot more," answered Renstoke
deliberately.  "Remember, we don't know anything positively yet.  I am
only giving you my personal opinion."

All agreed that Renstoke's plan was best.  But they had yet to learn how
far the appalling reality outstripped the horror of their suppositions.

The inquest, held the following afternoon, was almost formal.  There was
no real evidence, of course, as to how the unfortunate man was killed,
and what amounted to an open verdict was found.  Neither the doctor who
examined the body, nor the detectives from Glasgow who made every
possible inquiry, struck the chain of reasoning which had led Renstoke
to his strange theory, and it was generally assumed that MacPherson had
been killed by some ferocious dog which had been lurking unseen for
months in the wild country around Renstoke.

Next morning all four started for Lockie.  Erckmann's house, though only
ten miles away in a direct line, was at least thirty by road, and as the
day was fine they decided to motor for about five miles, leave the car,
and walk across country for the remainder of the distance.  It was this
decision which led them to the first strange clue in the solution of the
terrible mystery.

At the point where they left the car, the road, which had been leading
westward, made an abrupt turn at the summit of a desolate hill, and
stretched away southward as far as they could see.  Their destination
was further west, and as Dick ran the car on to the grass at the side of
the road, they prepared for their tramp.

They had walked some four miles over rough heather-clad country when
Renstoke pointed to a big building a mile away and facing the top of the
steep rise they had just breasted.

"That is Lockie?" he said.

For the most part, the country was dry.  Below them, however, was a
shallow valley, along the bottom of which a rippling burn wound its way.
Descending the hill they crossed the brook and soon found themselves at
a tiny bridge beside the only gateway they could see in the high stone
wall, surmounted by a formidable barrier of barbed iron, which
surrounded the building.

In response to Renstoke's knock the door was opened by an ill-favoured
individual, evidently a foreigner, who stared at them in blank surprise.

"I want to see Mr Erckmann; is he at home?"  Renstoke demanded.

The man made some reply in a language which neither of them understood.
Renstoke repeated his question.

Turning to a telephone which stood on a small table in the lodge the man
spoke a few words.  A moment later he signed to them to enter and
conducted them to the entrance door of the big house.

As they approached a big, powerfully built man, heavily bearded and
wearing round horn spectacles, met them on the steps of the front door.

Renstoke bowed courteously.  "Mr Erckmann?" he inquired.

"Yes, I am Mr Erckmann," was the reply.  "What can I do for you?"

Renstoke as briefly as possible explained what had happened.  Erckmann
listened patiently and carefully.  Only at the end of the story, when
Renstoke told him quite frankly his suspicions, the man's eyes hardened
ominously and his lips tightened under his heavy grey moustache.

"Yes, I have a gorilla," he admitted.  "But if you suggest that it has
escaped you are quite wrong.  It has never left its cage since it was
brought here, quite young, six years ago.  It would be a bad thing for
some one if it did," he added.

"May we see it?" asked Renstoke quietly.

"Yes--if you doubt my word," snapped the scientist.  He was evidently,
for some reason, much annoyed and was controlling himself with obvious
difficulty.

During the conversation Dick had once or twice glanced at Yvette and was
surprised at the fixity of the gaze she directed at Erckmann.  She was
regarding him almost as if fascinated, with every sign of horror and
apprehension.

Without further words Erckmann led the way through a small paddock to a
row of cages, heavily barred with iron, which stood at the rear of the
house.  Before one of the strongest he halted.

"There you are," he said grimly.

Inside the cage, erect on its hind legs, stood an enormous ape, shackled
by a huge chain round its neck to a heavy stake driven into the ground.
Nearly seven feet high, it was so horribly repulsive in its perverted
likeness to humanity, that Yvette, Dick, and Jules turned away sick with
disgust and horror.  It snarled and chattered at the sight of the
strangers.

Renstoke, however, carefully examined the monster.  But he soon realised
that this creature had certainly not been at large, at any rate for some
considerable time.

The clue had failed.  Whatever the truth might be it was clear the
gorilla could have had no part in the terrible tragedy of Alan
MacPherson.

"A wonderful specimen," said Renstoke, turning to Erckmann.  "Have you
had him long?"

"About six years," the scientist replied.  "Would you like to see what
it can do?"  Without waiting for a reply, he spoke softly to the raging
beast in some language the others did not understand.

Instantly the brute calmed down, shuffled to the bars of the cage and
laid its head on the ground close to where Erckmann was standing.  It
was just as though a dog were fawning on its master.  Erckmann
fearlessly thrust a hand between the bars and scratched the repulsive
head while the great ape lay with closed eyes evidently in keen
enjoyment of the sensation.

Still talking quietly in the strange language, Erckmann put the beast
through a number of tricks which it performed, clumsily, of course, but
with obvious understanding of what was required of it.  It was, as
Renstoke realised, a wonderful example of animal training, for the
gorilla is perhaps the most intractable of all living animals.

"Perhaps as you are here you would like to see the rest of my
menagerie," said Erckmann, as he led the way to a series of cages
adjoining.

They gazed in astonishment at what they saw.  There was a superb tiger,
several leopards of different species, and at least a dozen wolves.  The
animals were all clean and well cared for and it was obvious at a glance
that none of them could have been wandering for an indefinite period
about the country.

"I hope you are satisfied, Lord Renstoke," said Erckmann at last, "that
none of my pets is responsible for what has happened?"

"Quite," replied Renstoke.  "And I am sorry we had to trouble you.  But
I am sure you will understand why I came.  The affair is so mysterious
that I could not leave any possibility unexplored."  Erckmann had
puzzled them all.  The man was perfectly courteous and apparently quite
open in his replies to their questions.  None the less all sensed that
he was ill at ease and that he quite certainly resented their intrusion.

Yvette, more sensitive and keenly strung than the others, shuddered
violently as they left the house.

"That man is bad, all bad," she declared vehemently.  "He has the eyes
of the snake."  She had put into words what all had felt, yet had been
half ashamed to confess.  There was something repulsively snake-like in
the steady glare of Erckmann's eyes behind the thick round glasses.

"I confess I feel like Yvette," said Dick, "the man gave me the creeps."

Renstoke looked grave.

"He didn't strike me as being quite aboveboard," he admitted.  "At the
same time, I don't see what he has to conceal.  All the cages were
occupied and it is certain none of the animals had been loose recently,
and if one had broken out there is no reason why he should not say so.
But he may have another ape which he has not shown us?"

They walked a few hundred yards in silence until they had got to the
bottom of the hill and approached the little burn that ran down the
valley.  There was no path, and as chance would have it, they deviated a
few yards from the way along which they had come.  They were crossing
the brook when Yvette gave a slight exclamation.

"Oh, look here," she said.

The bed of the burn was stony throughout, but at one point, at the very
edge of the water was a tiny patch of sand, smooth and firm and hardly
larger than a handkerchief.  Yvette pointed to it.

There, sharply and clearly defined, was the unmistakable imprint of a
naked, misshapen foot!  It was human beyond all question.  It pointed in
the direction of the house they had just left, and it was dear that the
barefooted walker, whoever he may have been, had stepped from the
heather just on to the patch of firm sand and been carried by his next
stride through and beyond the rivulet on to the heather and stones where
no footprints would remain.  By some strange chance that one tell-tale
footprint had been left in perhaps the only square foot of ground for
miles where an impression could be left!

They examined the footprint with eager curiosity.  Evidently the walker,
or rather runner, had come fast down the hill, for the front part of the
foot was driven deeply into the sand while the heel was only just
showing.

"He must have been running," said Renstoke, "and what kind of man could
run over such a country as this?"

The question was natural, for the heather grew thick and deep round
there and they had found walking difficult enough; running would have
been out of the question for any of them.

They were puzzled by the strange footprint, but how little they guessed
that it held the key to the terrible tragedy of Renstoke!

Late that night, Renstoke, Dick, and Jules sat yarning in the great old
drawing-room at the Castle.  The night was close and sultry, with a
threat of thunder in the air, and the big French windows which opened on
to the spreading lawn were flung wide.

They were discussing Erckmann.

"I didn't like him," said Renstoke, "though it is recognised that he
possesses genius in a marked degree."

"Oh!  You've heard something then?" asked Dick quickly.

"Yes.  The general public know nothing of him, but I hear that he has an
amazing theory that it is possible, by an operation on the brain, to
abolish almost entirely the ordinary characteristics of a man or an
animal, and by the injection of an appropriate serum to substitute the
mental, and to some extent the physical, characteristics of another
species.  He believes that you can, for instance, take a puppy-dog,
operate on its brain, inject a serum prepared in some way from the brain
of a monkey, and the puppy will grow up with the mentality and habits of
a monkey and with its bodily characteristics so transformed that it can
do many things--such, for instance, as climb a tree--which no dog could
do.  I believe he has actually succeeded in doing this!"

"How weird and extraordinary!" remarked Yvette.

"More than this, he believes you could do the same with a human being--
destroy its human attributes and give it, for example, the ferocity, and
something of the speed, of a wolf or a tiger."

"How on earth did you learn this, Renstoke?" asked Dick.

"From perhaps the only person who ever knew Erckmann really well," was
the reply.  "Some years ago Erckmann was the resident doctor at a
lunatic asylum in Prague.  He made a particular crony of his chief
assistant, a young doctor named Chatry, who afterwards went to Canada,
where I met him.  Chatry told me something of Erckmann's views and
experiments.  I was, of course, tremendously interested, but I little
thought I should ever run against the man in the flesh.  Erckmann was
undoubtedly a very able man, but there was a scandal.  On some pretext
or other he performed a remarkable operation on an insane person.  The
patient, who had previously been quite tractable, developed
extraordinary characteristics.  He growled and snapped at all who
approached him, insisted on eating his food on the floor instead of at
table, barked like a dog, and finally would only sleep curled up on a
rug.  In fact, he developed strikingly dog-like habits.  How much of
anything Erckmann let out generally Chatry never knew.  But he was asked
to resign, and he left Prague."

"A very curious story!"  Dick remarked.

"Now Chatry had no doubt whatever on the subject," said his host.
"Amazing as it may seem, he was firmly convinced that Erckmann had
deliberately made this extraordinary experiment and that it had
succeeded.  Chatry died just before I left Canada, but before he died,
he gave me a little manuscript book in which he has related the whole
story.  I'll show it to you to-morrow."

They said good-night and went to bed, leaving Renstoke, who sometimes
suffered from insomnia, to read himself sleepy.

It was about two o'clock when Dick, who was a light sleeper, was roused
by a shout for help, apparently from the drawing-room which was directly
below his bedroom.  Instantly he sprang out of bed, and snatching up a
revolver, rushed downstairs.

But he was just too late.

As he entered the brilliantly lighted drawing-room he caught sight
through the open window of a heavy misshapen body disappearing into the
gloom beyond the bright patch of light cast by the electric lamps on the
lawn outside.

Renstoke lay on his back on the floor, dying beside his favourite chair.
Close by was the book he had been reading and on the carpet near it was
his pipe, the tobacco still smouldering.

Dick knelt hastily by the side of his friend and sought frantically to
revive him.  But it was in vain.  The young peer died in his arms.  It
was evident that he had been attacked without the slightest warning, and
mercilessly strangled.

And in the side of his throat, just above the jugular vein, was a deep
wound, horribly lacerated, from which the blood flowed in a heavy
stream.

The Castle was speedily aroused, and in a few minutes half a dozen men
were busily searching the surrounding country.  But it was in vain--the
mysterious assailant of the unfortunate Lord Renstoke had vanished
completely.

The following day Dick, Jules, and Yvette, almost overcome with grief,
were discussing the loss of their friend.

"There is some devilry at work," Dick declared.  "And I shall never rest
till it is cleared up, if I spend the rest of my life here."

Yvette burst into a furious philippic against Erckmann.  "That man is at
the bottom of it all," she insisted.

"But, Yvette," Dick remonstrated, "we have no kind of evidence of that."

"I don't care," she replied vehemently, "Erckmann knows all about it.  I
should like to choke it out of him," she ended viciously in French.

"Well," said Jules, "we can't go to Lockie and accuse him.  How about
trying a trap of some kind?"

"We might do it in that way," Dick admitted.  "But what kind of trap?"

Long and eagerly they discussed the matter, and at length a plan was
evolved.

The next morning brought them a visit from Inspector Buckman, one of the
ablest men of the Special Branch at Scotland Yard, to whom, utterly
baffled, the police had very wisely applied for help.  He was well known
to all of them as a keen, capable man of infinite resource and undaunted
courage.

Buckman listened closely while Dick ran over the story, putting in a
keen question here and there.

"We have got to keep the real facts quiet," he said at length.
"Erckmann must not suspect that we have the smallest inkling of the
evidence of Lord Renstoke's death.  I will fix that up with the
coroner."

It was an easy matter.  Renstoke Castle was a remote spot, and while the
affair, of course, could not be entirely concealed, it was a simple
matter to keep the exact details secret.  All the public learned was
that Lord Renstoke had been attacked and murdered presumably by a
burglar for whom a close search was being made.

But behind all and working in secret the keen brains of Dick, Yvette,
Jules, and Buckman were busy.

Two or three nights later the word went round to the scattered farms
that every single head of stock was to be driven in to the farms and
rigidly confined in the buildings from dusk to daybreak.  So far as they
could ensure it not a single living thing was at large.

Dick's trap was arranged on the hill-side a mile from Renstoke.

Four inches above the ground, in a circle fifty yards in diameter, ran a
thin electric wire supported at intervals on small insulated posts.
Just inside the circle, on the side away from Renstoke, a sheep was
tethered to a strong stake.  In the centre of the circle from a tall
pole hung a powerful magnesium flash, electrically connected so that it
would be at once exploded by any pressure on the encircling wire, and
momentarily light up with day-time brilliance a large patch of the
surrounding country.

As dusk fell, Dick, Yvette, Jules, and Buckman carefully crossed the
wire and took up their positions in the centre of the circle, lying full
length in the sheltering heather, and each with a revolver ready to
hand.  In a leash beside Dick lay Spot, his favourite Airedale, who
could be trusted to give warning of the approach of any intruder, and
afterwards to track him remorselessly.

As the leaden moments dragged by it grew darker and darker until the
country-side was plunged in pitch blackness.  The strain on the watchers
was terrific.  They could not smoke or talk, they hardly dared to move.

Hour after hour dragged by.  Midnight passed.  Dick, half asleep, was
gently stroking the back of the Airedale.

Suddenly he felt the animal stiffen, and the hair along its back
bristled ominously.  A moment later the dog gave a low, half-audible
growl and rose to its feet.  Instantly the party were keenly alert.

Dick clapped his hand over the dog's muzzle, and the well-trained animal
subsided into silence.  But Dick could feel that it was strainingly
alert; obviously it sensed an intruder.

Keenly at attention, with every faculty strained to the utmost, the
silent watchers heard not a sound.  But a few moments later there was a
vicious snap in the air above them as the magnesium flash exploded,
turning the inky blackness for a fraction of a second into a blaze of
dazzling light.

In that brief outburst of radiance the four caught a glimpse of a horror
that photographed itself indelibly on their memories.

Twenty-five yards away a bestial, hideous face loomed out in the glare
of light.  It was the epitome of all things evil, with wild matted hair,
staring eyes and a horrible misshapen mouth drawn back in a snarl which
showed two rows of monstrous teeth.  The body they could not see.
Apparently the creature was crouching in the heather so that only its
ghastly head was visible.

Had it been a wild animal not one of the four, their nerves
steel-hardened by the war, would have felt a tremor.  But that ghastly
face, vile and brutal as it was, was unmistakably human, and for an
instant the watchers were paralysed with uncontrollable terror.

But it was only for a moment.

Four revolver shots rang out almost simultaneously, fired in the
darkness at the spot where the apparition had appeared.  A crackling
volley followed as the four automatics were emptied.  Almost with the
last shot came a howl of mingled rage and pain from the darkness.
Evidently a bullet had got home.

A few moments later Dick, with Spot barking madly and tugging wildly at
his leash, had plunged into the blackness in hot pursuit at the fiendish
intruder.  Close behind him came Yvette, Jules, and Buckman.

The hunt had begun!

Of that wild dash across country in the darkness Dick afterwards
remembered but little.  Spot plunged ahead without hesitation and Dick
followed, intent only on making the best speed possible and careless of
constant falls as he stumbled blindly along.  He dared not loose the
dog, for without it he would have been helpless, and he plunged blindly
forward, his reloaded pistol grasped in his right hand, careless of
himself and intent only on overtaking the horror which he knew lay
somewhere ahead of him.  Behind him toiled the others, guided by Spot's
frantic barks.

Progress, of course, was slow; falls and stumbles every few moments
checked the pace; the darkness was baffling.  It was with feelings of
intense relief that Dick at length saw the silvery edge of the moon
lifting itself above the hills behind him.  He had lost all sense of
direction, but the moon rising behind him told him he was travelling
westward.

Half an hour later the country was bathed in soft light and Dick was
able to pick up his bearings.  Suddenly he realised with a shock that he
was heading straight for Lockie!

Dick halted to let the others come up.  Without being afraid he felt
instinctively that something terrible lay ahead of them and that for
safety's sake it were best that they should be together.

They were a sorry-looking party--hatless, their clothes torn, their
faces and hands bruised and scratched by constant falls, almost
exhausted by their tremendous efforts.  But none of them thought of
giving up the chase.

For another mile they pushed onward, making better progress in the
growing moonlight.

Suddenly Buckman gave a tremendous shout.  "Look there!" he roared,
pointing to a low hill which ran across their path.

Not five hundred yards away, on the top of the rise and clearly
silhouetted against the sky, they caught a glimpse of a monstrous figure
which, even as they looked, vanished over the crest and was gone.  It
was, unmistakably, a man of giant stature!  It moved stiffly as though
in pain; evidently one of the shots fired in the trap had got home.

They hurried on.  When they reached the crest of the rise Lockie lay
before them, and they could see the monstrous figure crossing a tiny
stream in the valley below.

They were gaining rapidly now.  Dawn was breaking and the cold pale
light allowed them a dear view.

The creature ahead of them was toiling painfully up the slope which led
to Lockie.  Suddenly a man issued from the house.  It was Erckmann and
in his hand he carried a formidable whip.

Less than two hundred yards away Dick and his companions halted
spellbound.  In some mysterious fashion they realised that they were to
witness the last act in the terrible drama.

The end came swiftly.  More and more slowly, almost crawling at last,
the strange creature approached Erckmann and at length, evidently
utterly exhausted, collapsed at his feet in a heap.

They heard the scientist shout something unintelligible.  Then he raised
his heavy whip and struck with fearful force at the unfortunate thing
which lay before him.

It was a fatal mistake.  With the speed of lightning the misshapen heap
on the ground flashed into furious activity.  All the horrified
spectators saw was an instantaneous leap and a brief struggle, and
Erckmann and the Thing locked in a deadly grapple and then drop
motionless.

Dick covered the last hundred yards in a furious dash.  But he was too
late.  Erckmann lay dead, with his adversary dead on top of him.  The
zoologist had been killed almost instantly by the grip of two large
hands that still encircled his neck in a vice-like clutch, and in his
throat the misshapen fangs of the creature were still buried deeply.
Only with infinite trouble was the body of the scientist freed from that
deadly grapple, and they were able to examine the monster that had
spread terror and death through Argyllshire.

Unmistakably the body was that of a man, but incredibly dehumanised and
ape-like.  The muscular development was tremendous; the hands and arms
were knotted masses of titanic muscle.  But the crowning horror was the
face--low-browed, flat-nosed, with a tremendous jaw and long pointed
teeth, utterly unlike anything human.  The body, stark naked, was
covered thickly with hair and in the side was a terrible wound evidently
made by the impact of a soft-nosed bullet from one of the automatic
pistols.  No normal human being could have survived it for more than a
few minutes.

It was only later, when they searched Lockie, that they realised fully
that Erckmann had fallen a victim to a monster he had himself created.
His diaries proved that Chatry had spoken the truth.  They were a
repellent but horribly fascinating account of his experiments.  Of the
results he had written in a wealth of detail, but of the process he
employed there was not even a hint.  That awful secret he had kept to
himself, and had taken with him to his grave.

They found that he had, as Chatry had said, taken a human being,
obviously of low mental development--possibly an asylum patient--and
practically, by some devilish discovery, converted it into a human ape,
endowed with the blood-lust of the tiger.  But whether the fearful
creature was capable of receiving and acting upon instructions, or
whether Erckmann simply let it loose to follow its terrible instincts
until the "homing" instinct brought it back they never learned.

Of Lockie, the police decided to make a clean sweep.  The animals were
shot and the half-dozen evil-looking foreign servants were paid off and
sent to their homes, mostly in the wilder parts of Transylvania.  They
one and all refused to say a word.  Whatever they were, they were at
least faithful to their dead master.

Then, in the magnificent chemical laboratory with which the house was
equipped, Dick, who found himself Renstoke's sole executor, easily
arranged an "accident."  Fire broke out, there was no help for miles
around and in a couple of hours the ill-omened house was a heap of
ashes.  The Spectre of Lockie had been finally laid.

CHAPTER SEVEN.

THE PERIL OF THE PREFET.

It was a mystery of the City of Paris which engaged the trio--a secret
that has never been told, though many enterprising newspapers have tried
to fathom it.  Here it is related for the first time.

On a gloomy mid-December morning the sensation-loving Parisians awoke to
a new and eminently agreeable thrill.  It was only last year and the
occasion will be well remembered.

There had been trouble enough in the City of Light, which for once at
any rate belied its name.  A series of strikes had half-paralysed the
capital.  Coal and light were almost unobtainable; the public lamps
remained unlit; at night the City of Pleasure was plunged in profound
gloom.  There were misery and wretchedness in the haunts of squalor and
poverty which flanked the wealthier districts where, at a price, all
things agreeable were as usual obtainable.

But the dumb underworld was becoming vocal!

"A Mort L'Assassin!"  At daybreak the startling legend suddenly, and
without warning, revealed itself from a thousand vantage-points to the
awakening city.  In crude, blazing red it flared from the hoardings--
sinister, ill-omened and, above all, full of significance.  Parisians
alone knew.

There could be no possibility of doubt as to the individual referred to.
It was, beyond question, Raoul Gregoire, the Prefect of Police, whose
cold, ruthless vendetta against the dark, turbulent forces which flowed
beneath the effervescent gaiety of the gay life of Paris, had earned for
him the vindictive hatred of the criminal world, and had gained him his
unenviable sobriquet of "Assassin!"

For months Raoul Gregoire's life had hung by a thread.  Before his
appointment he had been Prefect of Finisterre.  A series of efforts to
"remove" him had been defeated only in the nick of time.  Twice he had
been badly wounded.  Once a bomb had wrecked his car just after he had
left it.  A less courageous man would have given up the unequal contest
and sought a pretext for retirement--back to the quiet, sea-beaten coast
of Finisterre.

But Monsieur le Prefet was of a different mould.  Stern and ruthless he
was, but his courage was invincible.  He remained calm and imperturbed--
far more so, indeed, than many of his subordinates, who feared that the
vengeance of the underworld might fall, by accident or design, upon
themselves.

"Gregoire has pushed things a bit too far," was Yvette's verdict, as she
talked over with Dick Manton and Jules the latest and most blatant
challenge to the forces of the law and order.  "They mean to make
certain this time.  I'm sure of it?"

"It certainly seems so," Dick agreed.  "But I wonder when and how it
will be?  That's the point.  Gregoire doesn't show himself much in
public now; he is practically living in the Prefecture, and surrounded
by his agents he is far too well guarded for any attempt to be made
there."

"They will have a good chance at the Sultan's reception," remarked Jules
reflectively.  "Monsieur le Prefet will have to be in the procession--he
can hardly stay away even if he wanted to.  It would show the white
feather."

It was a day to which the gaiety-loving Parisians were looking forward
with special interest.  France's age-long quarrel with the wild tribes
of the Morocco hinterland had at length been amicably settled, and their
Sultan, Ahmed Mohassib, a picturesque figure whose eccentric doings
provided the gossip-loving boulevard with hundreds of good stories, was
"doing" Paris as the guest of the Quai d'Orsay.  It was expedient to
show the barbaric ruler all the honour possible, and the following
Friday was the day on which he was to pay a ceremonial visit to the
Elysee.  There was to be a great procession, and the Government had let
the Press understand that a skilfully worked-up popular demonstration
was desirable.  The papers had responded nobly, and it was certain that
"tout Paris" would be out to see the show.

On the occasion, at any rate, Monsieur le Prefet must be greatly in
evidence.  He was responsible for public order and must ride in the
procession whatever the risk to himself, a plain target, for once, for
the bullet or bomb of the assassin.

"To-day is Saturday," Yvette remarked.  "We really have not much time to
spare between now and the twenty-second.  I think I will make a few
inquiries to-night.  Jules had better go with me."

Dick's heart sank.  He knew what Yvette's "inquiries" meant--hours,
perhaps days, spent in the lowest quarters of Paris, surrounded by such
horrible riff-raff that if her purpose were even suspected her life
would be worth hardly a moment's purchase.

But he knew it was useless to remonstrate.  Yvette had a perfect genius
for "make-up," and what was far more important, a perfect knowledge of
the strange _argot_ which served the underworld of Paris.  Jules was
almost as clever as Yvette.  But in this particular, of course, Dick was
far behind.  He could not hope to sustain his part in surroundings where
a single wrong word would mean instant suspicion, and probably a swift
and violent death for all three.

"I wish I could go with you, Yvette," he said wistfully, "but, alas!  I
know it is quite impossible."

Yvette had many friends in the lower quarters of the Montmartre.  The
proprietors of many of the low _buvettes_ of the slums--places where one
could get absinthe and drugs--were secretly in her pay, and so far as
they were concerned she had no fears; the traffickers trusted her
because they knew their secrets were safe.  And by an ingenious code
system which depended upon a mere vocal inflexion of certain common
words she could reveal her identity, no matter what her disguise, to
those who were in her secret.

Darkness had fallen upon the city when two appalling specimens of the
worst vagabondage of Paris--a man and a woman--crept silently through
the market quarter towards one of Paris's vilest haunts of villainy.
They were such woebegone specimens of humanity as might have served for
figures in some new "Inferno."  Bedraggled and unkempt, their hands and
faces besmirched with grime, their clothes hanging in tatters, it would
have been impossible for even the keenest eye to have detected the smart
French girl and her usually debonair brother.  So far as appearances
went they were safe enough.  The risk would come when they began to
talk, and especially when they began to ask questions.  Here a slip of
the tongue might betray them.  But the risk had to be taken.

The Prefet himself, quite as anxious as Dick for the safety of Yvette
and Jules, had taken precautions to protect them as far as possible.
Actual escort, of course, was out of the question.  Both Yvette and
Jules carried revolvers, but in addition Jules had concealed in the
ample pockets of his villainous clothing, a tiny but delicate wireless
telegraph apparatus, powerful enough upon a dry battery to send out a
wireless wave which would carry a thousand yards or so.

This dainty little bit of electrical work was the invention of Dick
Manton.  Hardly larger than an old-fashioned watch it was operated by a
hundred-volt battery which fitted into a specially made pocket, and the
tiny transmitting key could be operated with one finger without arousing
the slightest suspicion.  Gregoire's agents were dotted thickly around
the unsavoury neighbourhood, each in touch, by means of the wireless,
with every movement Yvette and Jules might make.  Dick himself was not
far away.  How amply these precautions were justified the events of the
night were to show.

For hour after hour Yvette and Jules slunk from one haunt of vice to
another, always keenly on the alert, frequently helped by one or another
of Yvette's disreputable friends, but yet unable to pick up the
slightest vestige of the trail of which they were in such active search.

At length their patient vigil culminated.

Plunging deeper and deeper into the labyrinth of the slums, they had
penetrated at length to a tiny bar in the very lowest and most dangerous
portion of the market section.  The place was crowded with a mass of
riff-raff at which even Yvette and Jules, accustomed as they were to
such sights and sounds, could not repress a shudder.

The proprietor, as it happened, was a beetle-browed Provencal whose one
redeeming feature was gratitude to Yvette.  His character was utterly
bad and he had been mixed up in dozens of affairs more or less
disreputable.  A year or two before a serious charge of which he
happened to be innocent had been brought against him.  Yvette had
managed, with considerable trouble, to lay the real culprit by the
heels, and Jules Charetier, Apache though he was, would now go through
fire and water to serve her.  Yvette knew that in his house she was
personally far safer than she would have been in many more pretentious
establishments.

Charetier raised his eyebrows when he caught the slight inflexion that
instantly revealed to him Yvette's identity.  But he took no further
notice beyond serving the drinks for which she had asked.

A moment later, with a significant look, he quitted the room.  Yvette,
with a slang caution to look after her drink for a moment, slipped into
the filthy street and round the corner to the side entrance of the
house.  Charetier was waiting for her, and a few moments later they were
seated in the man's dingy room on the floor above the bar.

"Whatever are you doing here, mademoiselle?"  Jules burst out
impulsively.  "This is no place, even for you!"

"Listen, Charetier," replied the girl rapidly.  "Something is brewing
for next Friday.  Something serious!  You have seen the posters.  I
_must_ find out about it.  Can you tell me where any of the `Seven' are
to-night?"

Jules Charetier paled at the mention of "The Seven," the powerful
camarilla whose hidden influence was felt throughout the criminal
underworld of Paris, London, and New York.  The men who, practically
without risk to themselves, were responsible for half the anarchist
crimes of the three great capitals.  Who they were, and their real
names, not even Yvette knew.  Never appearing directly themselves, they
worked entirely through agents, and fighting against them, the police
found themselves in a stifling fog of mystery.  But, as Yvette knew,
Charetier was deep in the councils of Continental Anarchism, and she
knew, too, that in his hands the life of the ordinary police agent would
have been worth nothing.  Even for herself she was not very confident,
but she had decided on a bold stroke, trusting Charetier with everything
on the ground of the service she had done him.

At first the man was obdurate.

"Not even for you, my dear mademoiselle," he said sullenly.  "But,
mademoiselle," he went on earnestly, "we have been friends, therefore I
implore you for your own sake to drop the matter and get away as
speedily as possible.  I cannot tell you anything."

Yvette's revolver flashed out and in an instant she had the innkeeper
covered.

"Listen, Jules!" she cried imperiously.  "My brother is below, and the
house is surrounded.  If I stamp upon the floor you will be raided
instantly.  And you know there are things here you would not like the
police to see--they don't know it, but you and I do!  Suppose Demidoff
learned that his papers had fallen into Raoul Gregoire's hands--eh?"

For a moment Yvette thought Charetier would have risked everything and
sprung at her.  But it was only for a moment.  Then he collapsed.  It
was evident he feared Demidoff, the notorious Bolshevik agent, even more
than he feared the police.

"Very well, mademoiselle," he replied, beads of perspiration standing
out upon his wide white forehead and, despite his bravado, a hunted look
crept into his eyes.  "You might try the `Chat Mort.'  There will be a
meeting there at three o'clock this morning.  But again I implore you
not to go.  You cannot get in and if you did you would never come out
alive."

"In which room do they meet?" was Yvette's only reply.

"The one at the back, looking out upon the old courtyard," was
Charetier's reply.  "I know no more than that."

"Thanks, Charetier," said Yvette as she rose to go.

"But, my dear mademoiselle," implored the innkeeper, "you will not
breathe--"

Yvette cut him short.

"That's enough, Charetier," she said in a freezing tone.  "You surely
know you are safe so far as I am concerned.  You have done me a great
service to-night and I shall not forget."  Five minutes later Yvette and
Jules were hastening to the "Chat Mort," a tavern of a gayer night-life
than the one they had just quitted.  It stood on the corner of two
filthy slums in the Villette Quarter and at the rear was one of those
tiny courtyards which so often go with old French houses--a place given
over to the storage of odds and ends of flotsam and jetsam which are
hardly worth the trouble of keeping, or even stealing.  Only a rickety
wooden fence divided it from the horrible alley deep in mud and refuse.

They realised at once that to enter the house would be impossible.  It
was now long past two o'clock and the street was deserted; everything
was silent as the grave, and from the closely shuttered "Chat Mort"
there was not a glimmer of light.  To all appearances the inhabitants
were soundly asleep.

But Yvette placed implicit trust in Charetier.  She was sure that the
mysterious meeting would be held at the appointed hour.

They crept silently to the rear of the building, cautiously forced a way
through the crazy fence, and a moment later were outside the window of
the room which Charetier had indicated as the meeting-place.

Crouching beneath the window they listened intently.  They were safe
enough except for some unforeseeable accident.

There was no sound in the room; no glimmer of light through the
shutters.

Jules took from his pocket a tiny drill which speedily and silently bit
a half-inch hole through the rotting woodwork of the window.  Into this
he thrust a plug which at the end bore an extremely delicate microphone
receiver.  With telephones at their ears they listened intently.  Not a
word would be uttered in the room without their knowledge.  They could
see nothing, but if anything was whispered they would certainly hear it.

The minutes dragged slowly past until just before three o'clock a slight
sound caught Jules' attention.  Some one had entered the room.  A moment
later came the rasp of a match being struck.

Three o'clock boomed from a distant church dock.  Footsteps echoed
inside.  The meeting was assembling!

How they longed to see into that room of mystery!  But that was
impossible; they must rely upon the microphone alone for all the
information they could obtain.  Jules' hand sought Yvette's wrist, and
in the Morse code he tapped out with his fingers--he dared not speak--a
caution to listen acutely.  Their only hope of identifying the criminals
was by their voices.

They could see nothing.  They could not even tell how many people there
were in the room.  But the mutter of conversation in varying tones came
dearly to their ears.  It consisted mainly, as they expected, of fierce
denunciation of Monsieur le Prefet of Police, whom they named "the
Assassin."

Soon it became clear that the meeting had been called solely to settle
the time and place of the attack; evidently the method had been decided
upon earlier.  Not a single word could the listeners catch of how the
attack was to be carried out, whether by bomb, or bullet, or knife.
Little did they guess the secret and deadly swiftness of the anarchists'
plan.

For some time the discussion continued.  Place after place was suggested
and rejected upon one ground or another.

Suddenly a hard masterful voice cut across the talking.

"The Place d'Italie will be the best," it declared.  "Half the road is
up there and the procession must go along the Avenue des Gobelins, close
to the old villa.  At that distance it will be impossible to miss.  And
there will be no noise and no fuss till the job is done."

The Old Villa!  Jules knew the place well--an ancient building dating
back to Louis XV, solidly built, and with all the quaint architectural
features of the time.  Quite unsuitable for any modern purposes, its
vast apartments had by degrees been turned into a queer medley of rooms
which served partly as flats and partly as offices to a heterogeneous
mass of tenants, many of them of more than doubtful reputation.  But how
any attack on Raoul Gregoire could be projected from a building which it
was certain would, on the day of the procession, be packed with
sightseers, Jules was at a loss to conceive.

That, however, remained to be discovered.  For the moment the important
thing was to capture the band of conspirators before they could make
their escape.

Jules withdrew, and adjusting his portable instrument--a marvel of
compactness--placed his foot against an iron lamp-post to make an earth
contact, and swiftly called the Prefecture of Police by Morse.

The telephones were on his ears, and almost next second he heard the
answering signal.  Then he tapped out on his wireless transmitter an
urgent message.  A moment later he and Yvette had slipped clear of the
place, and ran swiftly away.  It was no part of their plan to risk
recognition by any of the prisoners.

At the head of the alley they waited for about six or seven minutes,
when they met Roquet, the inspector of the Surete, who was in charge of
the detectives who were rapidly converging on the inn.  To him Jules
briefly explained the situation.

"We have them safely enough," declared Roquet with a strong accent of
the Midi.  "Every approach has been guarded for the last hour, and no
one has been allowed to pass in or out.  You can now leave it to us,
m'sieur."

Yvette and Jules were glad enough to say _au revoir_ and to hurry home
for a much-needed rest.  They could examine the prisoners at their
leisure at the Prefecture and, if possible, identify them by their
voices.

But a startling surprise awaited the detectives.

Their imperious knocking at the door of the frowsy Chat Mort at first
brought no reply.  A few minutes later the proprietor appeared,
half-dressed and yawning drowsily as though just awakened from profound
sleep.  He was instantly arrested and handcuffed and the police poured
into the house, revolvers drawn and ready for what they expected would
be a furious combat with reckless and desperate men.

To their utter amazement the house was empty!

The room looking on to the courtyard, in which, according to Jules and
Yvette, the conspirators had held their meeting, was in perfect order,
apparently as it had been left the night before when the place was shut
up.  There was not a sign that anyone had been there for hours, not even
a whiff of fresh tobacco smoke to suggest that the room had been
recently occupied.

Roquet was utterly mystified.  He had, with very good reason, dreamed
any escape impossible.  Could Jules and Yvette have been mistaken?

That, he felt, was out of the question.  None the less the problem
remained--where were the men?  The house was speedily searched from
attic to cellars, but in vain.  There was not the smallest indication
that any meeting had been held there!

Roquet naturally felt intensely foolish, and his embarrassment was in no
way lessened by the voluble protestations of the proprietor who
demanded, with every show of righteous indignation, the reason of what
he was pleased to term "an outrageous domiciliary visit."  There was, of
course, no charge against him, and ultimately the baffled police were
compelled to release him and retire, furious and puzzled at the utter
failure of what had promised to be a brilliant _coup_.

Three days later the mystery was solved.

From the cellar of the "Chat Mort" a narrow tunnel had been driven to an
equally disreputable establishment a short distance away, and when the
police had raided the house the plotters had swiftly bolted, leaving the
innkeeper to drop behind them the stone slab in the cellar floor which
covered the entrance to the tunnel.

The position now was grave enough, and Yvette, Jules, and Dick discussed
it at length with the Prefet and his lieutenants.  To all entreaties
that he should stay out of the procession the Chief resolutely turned a
deaf ear, and they found it impossible to shake his resolve.

Would the conspirators stick to the arrangement made at the "Chat Mort,"
or would they, alarmed by the raid on the house, make an eleventh-hour
change in their plans?  That was the problem to be solved.

Monsieur le Prefet was living on the edge of a volcano, and all his
precautions would, he feared, be of no avail against them.

Dick felt convinced they would carry out the plan arranged.  It could
not be imagined, he argued, that they would dream they had been
overheard, and it was evident that the plan had been very carefully
considered.  Ultimately it was decided to relax none of the ordinary
precautions, but to keep a specially close watch on the old villa in the
Place d'Italie.  Dick decided that, whatever the police did, he would
make his own arrangements for that purpose.  The sequel proved that it
was well he did so.

On the night prior to the procession the police carried out a very
drastic _coup_.  Every known anarchist in Paris was arrested on some
pretext or another and locked up.  One by one they were briefly
interrogated, while Jules and Yvette, concealed in the room behind a
screen, tried to recognise any of the voices they had heard in the Chat
Mort.

Fifty or sixty prisoners had been interviewed before Jules and his
sister standing behind a screen heard a voice they recognised.  It was
that of the man who had suggested the old villa in the Place d'Italie as
a suitable base for the attempt on the Prefet.  None of the others could
be identified, and it was evident that the worst of the miscreants were
still at large.

The man whom they recognised proved to be Anton Kapok, a Hungarian of
whom nothing was known except that he was in the habit of delivering
violent harangues at Socialist and Anarchist meetings.  But it was
evident now that he was far more dangerous than the police had hitherto
supposed.

Closely interrogated, he denied everything.  He knew nothing, he
declared, of the "Chat Mort" and had not been mixed up in any
conspiracy.  His Anarchist proclivities, however, he boldly admitted and
declared that the police knew all there was to know about him.

To the police a search of Kapok's room in Bellville revealed nothing
more incriminating than a mass of Anarchist literature.  But Dick made a
discovery which they had overlooked.

Close to the ceiling, immediately above the fireplace, was suspended on
two hooks what looked like a rod from which pictures might be hung.  The
police had, in fact, so regarded it.  Dick never knew what aroused his
suspicions, but something impelled him to mount a ladder and fetch the
rod down.  Then he made a startling discovery.

The supposed rod was nothing less than one of the wonderful blow-pipes
used by some of the aboriginal tribes of South America and elsewhere to
shoot their poisoned darts with which they either fought their enemies
or killed dangerous animals.  One of the darts, a tiny affair fashioned
out of a sharp thorn with a tuft of cotton which just filled the tube,
was actually in position.

Instantly Dick's mind travelled back to the strange deaths nearly a year
before of two police officials who had been specially astute in the
anti-anarchist campaign.  Both had been found dead in lonely streets,
and in each case the only mark on the body was a tiny scratch on the
cheek which no one had dreamed of connecting with their inexplicable
death.  As Dick gazed at the deadly blow-pipe those scratches assumed a
new and sinister significance.

Carefully removing the dart, Dick hurried with it to the laboratory of
Doctor Lepine, the well-known toxicologist.

Doctor Lepine smiled.

"Lucky you didn't scratch yourself with it, Monsieur Manton," he said in
French.  "It would mean almost instant death!"

He listened gravely as Dick described the death of the two police
agents.  The doctor had been away in England at the time and had not
even heard of the circumstances.  But he hurried round to the Prefecture
with Dick and carefully examined the documents which dealt with the two
cases and described minutely the appearance of the bodies.

"I have not the slightest doubt," he declared, "that both men were
killed with one of these darts.  Every indication points to it.  But as
the darts were not found we must presume they were removed after death
to avoid arousing suspicion.  The victim would be paralysed almost
instantly, and would fall and die almost on the spot where he was
standing when the dart infected him.  If there are any more of these
accursed things in Paris it will, I fear, be a difficult matter to
protect Monsieur le Prefet, for a favourable opportunity must come in
the long run."

Dick hurried back to Kapok's room, meaning to secure the blow-pipe.  To
his amazement the deadly weapon had disappeared!  The police agents on
duty outside the room asserted that no one had entered.  But an open
window told its tale; some one had crept along the ledge outside,
entered the room and possessed himself of the weapon.

Dick spent several anxious hours with the Prefet, Raoul Gregoire, and
Inspector Roquet, arranging a plan of campaign.

Next morning found him crouched in an upper window of a locked room in a
house facing the old villa in the Place d'Italie.  Close at hand lay a
powerful pneumatic gun, a weapon perfected by Jules and almost as deadly
and efficient as a rifle.  He was haunted by a sickening _sense_ of
foreboding.  Against every evidence of his reason and senses he felt
convinced that it was from that old villa that danger threatened
Gregoire.

Yet he was bound to admit that his fears seemed absurd.  The old house
opposite was packed with sightseers, but there was a detective in every
room close to the window.  Even the garrets had been searched.  It was
obvious that they had not been entered for months.

Yet Dick could not shake off the uncanny feeling which haunted him.

At last the head of the procession came in sight, with the blare of
military bands and a crash of cheers from the thousands of spectators
lining the streets.  But Dick had no eyes for the show.  His whole
attention was riveted on the building before him.

The Sultan Ahmed Mohassib, of Morocco, in his white _burnous_ with many
decorations, passed amid a hurricane of cheers.  Glancing along the
procession Dick saw the Prefet--a soldierly figure sitting erect in his
car.  In a few moments he would be abreast of the villa.

Suddenly Dick's eye was caught by a flash of light.  Glancing quickly
upward he saw to his amazement that the window of a garret facing him--a
room which had already been searched--had suddenly opened.  Only the
chance reflection of the sun upon the glass had attracted his attention
to the swift movement.

As Raoul Gregoire passed, a dark rod, clutched in a hand which rested on
the grimy windowsill, projected itself from the window.  It wavered for
a moment, then steadied itself and pointed downward.

Instantly Dick fired.

The hand disappeared with a jerk, while the rod slid forward and fell
over to the ground!

Wild with excitement Dick dashed down into the street.  It was utterly
impossible to force his way through the cheering crowd and he could only
watch Monsieur le Prefet in a fever of anxiety.

It was soon dear that Raoul Gregoire was untouched.  Evidently the
would-be assassin, if he had indeed dispatched one of the poisoned
darts, had missed his aim.

Five minutes later Dick and half a dozen detectives were in the garret
of the old villa.  But they were too late.  The bird had flown, badly
hurt to judge by the blood which stained the floor.  But on the
window-sill lay three little poisoned darts ready for use.

A glance at the open skylight in the low roof was enough.  In a moment
they were out on the roof of the adjoining house.

A few yards away was a rope ladder hooked over the parapet and dangling
to the exterior fire-escape leading from the roof of a big drapery store
only ten feet below.  The miscreant himself had vanished.

The would-be murderer, it was clear, must have climbed the fire-escape
during the darkness of the previous night, and lain hidden on the roofs
till the procession came along.  After the garret had been searched, he
had slipped down with impunity while every one was excitedly watching
the procession.

They never caught him.  But when Gregoire returned to the Prefecture a
poisoned dart was found sticking in the upholstery of his car, close to
his head.  Had it been a bare half-inch lower down it would, no doubt,
have struck him with fatal result.  Dick's lightning shot had spoilt the
miscreant's aim and saved the Prefet's life.

The incident is one of the secrets of the life of official Paris and led
to the Prefet's resignation a month later, an occurrence which filled
all France with dismay and was the cause of much conjecture and
speculation.

Raoul Gregoire has returned to the provinces and is now Prefet of the
Department of the Alpes-Maritimes an appointment which he much prefers.

CHAPTER EIGHT.

THE MESSAGE FOR ONE EYE ONLY.

The heat was stifling in the Gran Ancora at Barcelona, an obscure but
grandiloquently named cafe of more than doubtful reputation.  At
dilapidated tables in the long apartment which served as a saloon groups
of rough-looking men were drinking steadily.  The fumes of strong
tobacco poisoned the heavy atmosphere, flies swarmed over everything,
the air was full of the reek of stale drink and unwashed humanity.

Though it was but early evening the ill-omened place was already filling
up.  It was a notorious haunt of betting men and some of the worst
characters of the town, frequented by desperadoes who were ready to
undertake any deed of violence if it offered the promise of plunder.
The swarms of anarchists, who are the curse of Spain, found there a
ready welcome and congenial companionship.

At a table at one end of the long room, sat a solitary individual who
was reading the "Diario," an anarchist journal devoted to the preaching
of doctrine of the most revolutionary type.  He spoke to no one, and no
one spoke to him, though now and again curious glances were directed
towards him.  He took no notice of the hubbub around him, but went on
calmly reading his paper and sipping slowly at a glass of the villainous
wine which seemed to be the favourite beverage of the habitues of the
house.

The stranger was no other than Dick Manton.  He had come to Barcelona on
the trail of a gang of international crooks who had got away with a
hundred thousand francs by a clever bank swindle in Paris.  Had his
identity been suspected his life in that haunt of depravity would not
have been worth five minutes' purchase.

But he sat there undisturbed, apparently oblivious of what was going on
around him, but in reality keenly on the alert and with one hand close
to the butt of the heavy revolver which, as he well knew, he might be
called upon to use at any moment in the deadliest earnest.

Manton stiffened suddenly as his eye fell on the queer jumble of figures
quoted above.  They were buried away in a mass of advertisements and
might well be overlooked by the casual reader.  As Dick well knew, the
"Diario" was used for all kinds of queer communications to all kinds of
queer people, and he was attracted by the hint of mystery, a lure which
he could never resist.  The jumble of figures fascinated him.  He had a
strange feeling that it would be well worth while to try to decipher the
weird cryptogram.  But he knew better than to try to do so there.  It
was not healthy to try in public to pry into the secrets of the
underworld of Barcelona.

Dick Manton had had a strange and adventurous career.  But as he gazed
at the odd announcement, he had a premonition that he was on the edge of
a mystery stranger than anything that he had so far encountered.

Having read the queer cryptogram over and over again, Dick slipped the
paper into his pocket.

Presently he finished his wine and sauntered out, with an uneasy feeling
that made him wonder whether he would reach the door without a bullet in
his back.  He got out in safety, however, and once clear of the doubtful
neighbourhood of the cafe, made his way swiftly to his rooms at the
"Hotel Falcon."

It took several hours of hard work before he could obtain the key of the
cipher.  Then he realised with a gasp that it was in one of the simplest
of British signal codes.  The key read:

At first Dick was completely mystified.  The message conveyed nothing to
him.  Who were Mataza, Wilson, and Greening?  Where was Chalkley?  And,
above all, why should such a message appear in an English code in an
obscure paper published in Barcelona?

It was the last point which worried him most.

He felt instinctively that the message must conceal a meaning of which
he was necessarily ignorant, and that it must be related to some affair
which was pending in England.  The more he thought about it the more
uneasy he grew.  He had the premonition which so often comes to the help
of the detective, and at length, though he was almost ashamed of acting
on such slender grounds, he decided to consult his chief.  An hour later
he was on his way to Paris, leaving the affair of the bank swindlers in
the hands of a capable subordinate.

Arriving in Paris he drove straight to Regnier's private apartment, just
off the Place de la Concorde.

"Why, Manton, what brings you here?" asked Regnier in surprise.  "Have
you finished at Barcelona already?"

For answer Dick laid the deciphered cryptogram before the Chief.

"What do you make of that?" he asked abruptly.

Regnier read the slip of paper with knitted brows.

"Queer," he commented.  "Why should it be published in the `Diario'?  I
think it means mischief.  Do you know Chalkley?"

Dick shook his head.

"No," he replied, "but it sounds like an English name.  And yet I have a
feeling that I must have heard it somewhere.  It sounds familiar, but I
cannot place it.  In the meantime I will run home and see if the English
papers will tell me anything."

Dick found Jules and Yvette eager for news; he had telegraphed them that
he was returning.  Dick, Jules, and Yvette had become the most
formidable combination in the French Secret Service.  They always
insisted on working together, they would accept no assistance except
that which they chose themselves, and they would work only under the
direction of Regnier, who was astute enough to realise their abilities.
Yvette had been prevented by a slight illness from accompanying Dick to
Barcelona, and both she and Jules, who had stayed with her, hated
inaction.  There had been a slump in international crime of the kind in
which they specialised, and they were suffering from _ennui_.  Anything
which promised excitement and adventure was welcome.

They listened eagerly while Dick told his story.

"And now," said Dick, half ruefully, as he concluded, "I don't know
whether we are on the track of something or whether I have been an
idiot."

Yvette's eyes were dancing with merriment.

"Well, Dick," she said, "you are certainly a pretty Englishman not to
know one of the most famous places in your own country.  Don't you
really know Chalkley?"

"No," replied Dick in bewilderment.  "What do you know about it?"

For answer Yvette rummaged among a pile of newspapers and produced a
copy of the "Times" dated a week before.

"There?" she said.  "Read that."

"That" was a closely printed column which Dick proceeded to scan with
attention.  It was an article describing the wonderful deposits of
pitchblende, the ore from which radium is extracted, which had been
discovered in the Ural region in the neighbourhood of Zlatoust.  An
English combine had secured the monopoly of the working for fifteen
years, and already a supply of radium valued at one hundred and fifty
thousand pounds had been brought home by the famous Professor Fortescue
for the use of British chemists and medical men.

The discovery and acquisition of the monopoly by British interests, the
article pointed out, had put England far ahead in the field of radium
research, for she had now a big supply of the precious commodity at her
disposal, while other nations were struggling along with the tiny
quantities obtained from other and far less rich deposits.  And, as was
fully explained, it was not in medicine alone that the radium would be
valuable; there was hardly a department of commerce, to say nothing of
the arts of warfare, in which radium was not playing a considerable and
constantly increasing part.  So many new discoveries were being made by
the band of experts, of whom Professor Fortescue was the acknowledged
head, that it was beginning to be realised that radium in the future was
likely to be as valuable as coal and oil had been in the past.

But--and here was the fact of most significance to Dick--the radium was
at Chalkley, Professor Fortescue's home in the wilds of the Durham
moors.  He had taken it there on his return from Zlatoust for use in
some critical experiments he had in hand before it was sent on to the
young but growing school of Medicine at Durham University.

They had at least approached the heart of the mystery!  It was evident
that some band of international desperadoes had designs on the precious
radium.  In spite of their enormous value, the two tubes containing the
salt could easily be carried in a man's pocket, and in Germany there
would be a ready market for it among the great chemical firms, whose
business consciences were sufficiently elastic to permit them to pay a
big price and ask no awkward questions.

Dick was reading the report carefully, when he suddenly gave a startled
exclamation.

"Why, look here," he said, "the radium is only to be kept at Chalkley
till the twenty-ninth.  That explains the twenty-nine in the
advertisement.  And to-day is the twenty-seventh.  If anything is to
happen it must be at once or they will be too late.  I must ring up
Regnier."  Regnier was with them in half an hour.  He was filled with
excitement when he learned the facts which Yvette had discovered.

"That," he said, "puts an entirely new complexion on the affair.  There
can now be very little doubt about the matter.  Clearly `lead' means
radium, and I think we can interpret `bull market' as an intimation that
it is a big prize.  They are evidently well informed, whoever they are.
We must tell London at once."

But before anything could be done a messenger for Regnier arrived post
haste from the bureau of the Secret Service in the Quai d'Orsay with
strange news.

A big aeroplane, flying at a tremendous speed, had crossed the
Franco-Spanish frontier near Bagneres de Luchon having apparently come
right across the Pyrenees.  It had ignored all the signals of the French
frontier guards, whose aeroplanes had, in consequence, gone up in
pursuit.  Only one of them was fast enough to approach the stranger, and
a fight had followed in which the French machine was crippled and forced
to descend.  Thereupon the strange machine had proceeded, flying in the
direction of Bordeaux.  Telephone messages had brought warning of its
approach, and several attempts had been made to stop it, but without
success.  It had been reported, chased by French aeroplanes over
Bordeaux, Nantes, and St Malo, and at the latter place, just as dusk
was falling, it had left the French coast and laid a course apparently
for England.  No further news of it had been received.

Regnier looked grave.

"Of course," he said, "we have absolutely no reason to couple this
machine with the advertisement in the `Diario,' but I confess I am
uneasy.  There is at Chalkley radium worth a fortune, easily carried if
anyone can get hold of it, and readily convertible into cash.  What
better device could be employed than a fast aeroplane which could get to
Durham and away before anyone could hope to stop it?  In any case, I am
going to telephone Scotland Yard at once."

Half an hour later he was in communication with Inspector Cummings, the
senior officer on duty at the Yard.  To him he explained his suspicions,
half afraid, with the Frenchman's dread of ridicule, that the other
would laugh at his story as an old woman's tale.

But Inspector Cummings was too experienced to be neglectful or sceptical
of anything which could disturb Regnier, whom he well knew to be one of
the most astute and level-headed of men.  He took the matter seriously
enough.

"We have heard nothing yet," he said.  "But I will 'phone Durham at once
and let you know in the course of an hour."

They waited anxiously for the reply.  It came at last.

"Cummings speaking," said the voice on the 'phone.  "I have spoken to
Durham.  They have heard nothing there, but they are unable to obtain
any reply from Professor Fortescue.  The telephone exchange reports his
line out of order.

"But here is a queer thing.  A big aeroplane, evidently a foreigner, was
reported this morning to have been seen over the Midlands flying north.
There was a lot of mist about, and we have not been able to trace the
machine yet.  But it was certainly not one of ours."

"Well," said Regnier, "will you keep me posted?  I fancy you will have
more news before long.  In any case, you will have Durham warned?"

"I have warned them myself," replied Cummings, "and they are sending a
couple of men out in a motor to make inquiries.  You know Chalkley is
about twenty-five miles from Durham and quite in the wilds.  Professor
Fortescue was, a couple of years ago, carrying out some experiments in
which it was absolutely necessary he should be away from anything like
traffic vibrations, and he chose this place for the purpose because it
was remote from any railway or heavy traffic.  He has stayed there ever
since; he said it suited him to be `out of the world,' as he called it."

Three hours later came still more startling news.

The police officers who had gone from Durham to Chalkley had found that
two armed men had made a raid on Professor Fortescue's house.  They had
gagged the servants, who were found lying bound and helpless, and the
Professor himself was found lying unconscious in his laboratory, having
apparently been sandbagged.  The raiders had leisurely helped themselves
to food, and, having cut the telephone wires, had departed without any
particular haste.

But the great leaden safe, weighing several hundredweights, in which the
precious radium had been brought to England, was found to have been
broken open.  _The radium was gone_!

Nothing in the meantime had been heard of the strange aeroplane.  But a
few hours later an old shepherd walked into one of the local
police-stations and told a queer story.

His sheep the previous evening, he reported, had been disturbed by the
passing of an aeroplane which, flying very low, had landed on the moors
a few miles away from the Professor's house.  It had stayed there all
night and, so far as he knew, was still there.  He had been unable to
approach it closely as it was separated from where he had been by a deep
gorge and a stream which he could not cross without making a detour of
several miles.  He had seen two men near the machine who had walked away
and disappeared in the folds of the moor.

A strong party of police, Cummings added, had left at once for the spot
where the aeroplane had been seen, taking the shepherd with them as
guide.  The place was remote from any road, and it would be an hour or
two before they could get there.  But the Air Ministry had been warned,
and already aeroplanes were going up in the hope of locating the strange
machine.

"I must be in this," said Dick.  "Ask him if I can come over.  I cannot,
of course, go unasked."

"Of course," said Cummings in reply to Regnier's request.  "We shall be
only too glad to have Mr Manton.  Miss Pasquet can come too, if she
likes.  But I'm afraid he won't be able to get here in time.  We shall
either have got these fellows or lost them hopelessly in a few hours."

Dick turned to Jules.

"Ring up the British Air Ministry," he said, "and ask them if the
strange machine gets off the ground to send us every movement as it is
reported.  Keep the telephone on all the time.  I am going to try to cut
these chaps off with the Mohawk.  You will have to report to me by
wireless every movement as it comes through.  From what we have heard I
fancy there are very few machines in England fast enough to catch those
fellows if they once get started.  Of course you will come, Yvette?"

An hour later, Dick and Yvette, seated in the helicopter, were in full
flight for England.  Yvette was at the controls; Dick, in view of the
work that might be before them, crouched over the tiny machine gun which
peered from the bow of the machine.

------------------------------------------------------------------------

Professor Fortescue was in a terrible state of distress.  He had been
working in his laboratory, when a slight noise had caused him to turn
round.  A man, apparently a foreigner as the Professor judged from the
hasty glance he got at him, was standing close behind him.  Before the
Professor could speak or move he received a violent blow on the head,
and remembered nothing more till he recovered consciousness some time
later under the care of the police.

His chief concern was for the radium, and his distress at its loss was
pitiful.  It was a disaster from which he seemed unable to recover.  But
he appeared to derive a strange satisfaction from the danger in which
the thieves would find themselves.

"I don't know how they will get it away," he declared to the police
inspector.  "It was dangerous to stay very near the safe for long owing
to the terrible power of the radium rays.  If the thieves try to carry
the tubes in their pocket they will not get very far.  Surely they
cannot realise the terrible risk they are running.  However, that need
not distress us; all we want is to get the radium back."

In the meantime a strong party of police had arrived from Durham at the
Professor's house, and, under the guidance of the old shepherd, started
across the moors for the spot at which the strange aeroplane had been
seen.  It was slow going over rough and difficult ground which tested
the endurance even of the younger men.  The only unconcerned person was
the old shepherd who trudged stolidly on at a pace with which they found
it difficult to keep up.

They had gone eight or nine miles before the old man spoke.

"Not far now," he said.

A mile farther on he halted.

"It's just over yon hill," he said, pointing to a small eminence a few
hundred yards away.  "You will see it as soon as you get at the top."

Breasting the rise, the police cautiously approached the ridge and
glanced over.  There in the valley, only five or six hundred yards away,
was the aeroplane.  Two men in air kit stood beside it.

Scattering into a thin line the police rushed down the slope, every man
with a revolver ready in his hand.

But they were just too late.  They had only gone a few yards when the
men hastily took their places in the machine, there was a loud whirr as
the engine broke into action, and while the policemen were still a
hundred yards away, the strange machine rose into the air and was gone.
A furious volley rattled out from the revolvers, but the range was too
great and the breathless policemen had the mortification of seeing the
machine disappear rapidly to the south.

Immediately the fastest runner of the party started at a trot for the
Professor's house to send out a warning.  But it was not necessary.  The
aerodromes all over the kingdom had been warned by wireless from the Air
Ministry, and already a host of machines were scouting in every
direction.

The stranger, flying due south, had reached Bradford before he was
signalled.  Instantly there was a rush of aeroplanes from all parts of
the Midlands to cut him off.  But he slipped through the cordon, flying
very high and at a tremendous speed.  Outside Birmingham a fast scout
picked him up and reported by wireless, and from the huge aerodrome at
Cheltenham over twenty fighting planes leaped into the air to stop the
career of the marauder.

There was now no chance, at least, of his getting away unobserved.  He
was under constant observation, alike from the air and the ground, and
every moment wireless messages were pouring into the Air Ministry
reporting his progress.  But to catch him proved impossible.  Only two
of the pursuing machines were fast enough to keep up with the stranger,
and even they could not overtake him.  So the headlong flight went on,
drawing ever nearer to the southern coast.  If the stranger could get
out to sea all chance of stopping him would vanish.

But, unknown to the furious British airmen, help was close at hand.

Warned by Jules' wireless messages of the direction the strange machine
was taking, Yvette had steered a course to intercept him somewhere in
the neighbourhood of Bournemouth, and the Mohawk, with its wireless
chattering incessantly, was now swinging lazily at half speed in a big
circle between Salisbury and the Hampshire watering-place.

"Over Salisbury now," called Yvette to Dick, her voice ringing out
clearly above the muffled hum of the propeller, the only sound which
came from the helicopter, with its beautifully silenced engines.

A few minutes later Dick pointed to the north.  "Here he comes," he
shouted.

Far away were three tiny specks in the sky.

Through his glasses Dick could make them out clearly enough.  The leader
was a machine of a type he had never seen before; a mile behind it were
a couple of planes which he at once recognised as the Bristol fighters
which had been so familiar to him in France.

The pace of the three machines was terrific.  It was clear the English
airmen were going all out in a desperate effort to catch the stranger
before he reached the water, and they were expending every ounce of
energy.  But a moment or two later it was quite clear they were falling
behind.  Presently a puff of smoke from the leader signalled "petrol
exhausted," and he dropped in a long slant to the ground.

The second machine, however, held on grimly, though slowly losing
ground.  Evidently his predicament was the same as that of his
colleague, and a moment later he, too, dipped earthward and was out of
the fight.

Only the Mohawk stood between the stranger and safety!

But it was a Mohawk very different from the comparatively crude machine
of a year before, wonderful though that was.  Dick and Jules had worked
out a revolutionary improvement in the lifting screws, with the result
that a small supplementary engine, using comparatively little power, was
now sufficient to keep the machine suspended in the air.  As a result
the full power of the big twin driving engines was now available for
propulsion, and the speed of the Mohawk, when pushed to the limit, was
something of which Dick had hardly dreamed in his earlier days.  So far
as he knew the Mohawk was easily the fastest craft in existence.

But what of the stranger?  Had the men of the mystery craft a still
greater secret up their sleeve?  That they had something big Dick could
plainly see by the way the fastest craft of the British Air Service, the
best in the world, had dropped astern of the stranger.  Was the Mohawk
fast enough to beat the pirate?  They would soon know.

As the big machine came on, Yvette set the elevating propellers of the
Mohawk to work, and the helicopter shot upward.  The stranger saw the
manoeuvre and at once followed suit.  But here he was at a disadvantage.
Yvette's object, of course, was to get above him.  He would then be at
their mercy, for he could not fire vertically, while the gun of the
Mohawk was specially constructed so as to be able to fire downwards
through a trap which opened in the flooring.  If they could get what in
the air corresponded to the "weather gauge" at sea, they would have the
marauder at their mercy if the Mohawk had speed enough to hold him.
Could they do it?

Plainly the fugitive saw his danger.  As Yvette shot upward he must have
realised that in speed of climbing he was no match for his antagonist.
He decided to trust to his heels.

Yvette, climbing rapidly, had got a couple of thousand feet above the
stranger and was heading to meet him.  They were now twelve thousand
feet in the air.

Suddenly, with a tremendous nose dive, the foreign aeroplane slipped
below them.  The manoeuvre was so smartly carried out that Yvette was
completely taken by surprise, and before she could recover herself the
chance of bringing the stranger to battle had gone.  He had passed five
thousand feet below them, and the issue now depended upon speed and
endurance.

With a cry of disappointment, Yvette swung the Mohawk round in pursuit.
Their quarry, by his daring manoeuvre, had gained a couple of miles
before she could turn, and was fast disappearing towards the sea.

Dick shook his head.  He had seen the speed of which the fugitive was
capable, and he had the gravest doubts whether the Mohawk could equal
it.

Waiting for the strange aeroplane, Yvette had set the Mohawk to a
comparatively slow pace.  She had misjudged the distance and her error
had enabled the raider to get a more than useful--possibly a decisive--
lead.

But even as she swung round she had pressed the accelerator and the
Mohawk quivered as the big twin engines began to work up to their
maximum.  Watching keenly, Dick saw the apparent rush away of the
foreigner slacken and finally stop.  They were at least holding their
own.  He signalled Yvette for more speed.  She shook her head.

Dick was in despair.  The pace at which they were going was not enough.
He thought it was their best.  But he had not calculated on Yvette's
resourcefulness.

The French girl had swiftly made up her mind.  She knew they had plenty
of petrol for several hours' flight.  They were holding their own
already in the matter of speed, and the Mohawk, though Dick did not know
it, had still some knots in reserve.  Yvette would not jeopardise the
engines by instantly pushing them to the limit.

But they were "warming up" under her skilful handling.  They were two
miles behind as they passed over Bournemouth and started the long flight
to the French coast which the stranger was seeking.

Half an hour slipped by and Dick suddenly realised that the Mohawk was
gaining, slowly, it was true, but unmistakably.  He looked inquiringly
at Yvette, who nodded and smiled.

"All right, Dick," she shouted.  "We can get them any time we want."

Dick realised her plan.  His own thought, as a fighting man, would have
been to close at once and have it out.  But Yvette had the radium in
mind.  If they smashed the stranger over the sea the priceless radium
would inevitably be lost.

With the Mohawk gradually gaining, the chase drew near to the French
coast.  Cherbourg loomed ahead of them, drew near, and disappeared
beneath them.  They were over France.

Instantly Yvette began to coax the Mohawk to do its best.  Splendidly
the engines responded, the plane shot forward at a pace which surprised
Dick, and a few minutes later they were directly above the fugitive.
The battle was all but won.  In vain their quarry sought, by diving and
twisting, to shake them off.  His position was hopeless.

Seeing a good landing-place ahead Dick fired a couple of shots as a
signal.  They could see the terrified face of the passenger in the plane
below gazing upward at the strange shape of the Mohawk above them.

Then the signal of surrender came, and the fugitive dipped earthward.  A
couple of minutes later it came to land, and the two occupants stood
holding up their hands while the Mohawk came gently to earth fifty yards
away, dropping vertically from the sky in a fashion which caused the
pilot of the foreign machine the wildest astonishment.

The radium was saved!  But it enacted a fearful revenge.  The
unfortunate passenger, who they found out later was a well-known Spanish
anarchist, had imprudently placed the two tubes in his pocket,
apparently ignorant of their terrible power.  Even in the short time he
had them in his possession he was so terribly burned that he died a
couple of days later in spite of the efforts made to save him, while the
pilot, who had, of course, been near enough to the tubes to get some of
the effects, was also so seriously injured that for weeks his life hung
in the balance.  It was found impossible to remove the tubes to England
until Professor Fortescue, overjoyed at the good news, came bringing the
leaden safe into which the precious tubes were placed.

The sequel came a week later.  Not even the British War Office could
ignore the fact that the Mohawk, single-handed, had achieved a feat at
which the British Air Force had signally failed.  A highly placed
official sought Dick out.  The result was that the plans of the Mohawk
were sold jointly to England and France at the price of one hundred
thousand pounds.

And Regnier lost his "star" combination.  Dick had no longer before his
eyes the fear that had haunted him for so long that in marrying Yvette
he would be condemning her to a life of comparative poverty.  And so the
companionship born amid the stress and tumult of war came at last to
perfect fruition in the marriage between the two lovers which took place
in Paris just three months after their last air adventure.

------------------------------------------------------------------------

The End.