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                    INVADERS OF THE FORBIDDEN MOON

                         By RAYMOND Z. GALLUN

            Annihilation was the lot of those who ventured
             too close to the Forbidden Moon. Harwich knew
           the suicidal odds when he blasted from Jupiter to
          solve the mighty riddle of that cosmic death-trap.

           [Transcriber's Note: This etext was produced from
                      Planet Stories Summer 1941.
         Extensive research did not uncover any evidence that
         the U.S. copyright on this publication was renewed.]


"Calling the pilot of space ship X911!" Evan Harwich shouted into the
radio transmitter of his little Interplanetary Patrol Boat. "Good God!
Turn your crate back, you crazy fool! Don't you know you're headed
right into the danger zone of Jupiter's Forbidden Moon? You'll get
yourself burned to a crisp in another few seconds if you don't turn
back...."

Evan Harwich's growling voice was almost shrill at the end. His police
duties patrolling the vicinity of Io, innermost of Jupiter's larger
satellites, rarely developed moments as tense as this. Most other
pilots had brains enough to give the Forbidden Moon a wide berth. And
for excellent if mysterious reasons!

Yet the craft ahead, a sleek new job with the identification number
X911 painted on its conning tower, kept steadily on. Its slim hull,
which betrayed an experimental look, was pointed straight at the
threatening greyish disc of Io, the one world in the solar system which
no exploring ship of the void had ever reached--intact!

Almost everybody among the inhabited spheres knew about the dangers of
the desolate Forbidden Moon. Ever since the colonial empire of Earth
had been extended to the region of Jupiter and his numerous satellites,
Io had been a grim menace; sure destruction to any rocket that
approached within five thousand miles of its dreary, almost airless
surface.

Nobody seemed to know just why this was true; but some scientists
claimed that somehow there was an invisible layer or shell all around
Io; an immense blanket of strange energy or force that fused and
blasted the metal hulls of all ether craft that ran into its insidious
web.

Tensely and helplessly Evan Harwich watched, as the ship ahead
continued on its way toward what seemed sure catastrophe. No danger in
front of the recklessly piloted craft could be seen, of course. Five
thousand miles of clear, cold vacuum was all that was visible between
it and Io. But since this region held concealed in it all the potential
violence of a hair-triggered trap, ready to unleash a flaming death
that involved unknown physical laws and principles, maybe it wasn't
just plain vacuum after all!

With dogged persistence Harwich kept yelling futile warnings into his
radio. His shouts and curses were unheeded, and no answer was given. He
knew what was going to happen in another second. There would be a burst
of dazzling white fire all around the rocket of this foolhardy pilot
he had tried to save from suicide. Metal would drip and sparkle in the
absolute zero of space. In just another instant....

Harwich swung his patrol boat aside, not caring to end his own life.
But he kept watching the X911 from the side-ports of his cabin.

And now, something quite different from what he had expected was taking
place. Suddenly the apparently doomed ship was enveloped in a bluish
halo which seemed to emanate from a great helix or spiral of metal that
wrapped its hull!

Immediately afterward, as the X911 entered definitely into the zone of
destruction around Io, great white sparks lanced dazzlingly through
the blue halo. It was as though the latter was fighting back those
gigantic, unknown forces that had seemed to make the Forbidden Moon
forever inviolable. It was as though the halo was keeping the X911,
and whoever was flying it, safe!

Evan Harwich's slitted eyes widened a little in astonishment and hope.
"Dammit!" he grumbled happily. "That idiot's got some kind of new
invention that's protecting him! Maybe the Forbidden Moon is going to
be reached and explored after all!"

A second more that weird conflict of hidden forces continued. Watching
it was like watching a race, on which you have staked everything you
own. Visibly, that daredevil space ship seemed to slow, as if resisted
by a tangible medium. For an agonizing instant of suspense, Harwich saw
those wicked sparks brighten in the X911's bluish aura. Then the latter
dimmed, flickered, went out!

As if angry demons were waiting to pounce, destruction struck--quicker
than a lightning bolt.

       *       *       *       *       *

If there had been any humor in the situation before, it was gone now
utterly! The patrol man's lips dropped apart in sheer awe. The muscles
of his massive, freckle-smeared forearms tightened futilely as he
longed to help the X911's doomed pilot. In the pit of his stomach there
was a sickish feeling.

Where that rocket that had dared the inscrutable enigma of the
Forbidden Moon had been, there was a sudden, terrific blaze of light.
The intolerable incandescence of it seemed to reach out to infinity
itself, illuminating even the blackness between the distant stars of
space. But it was all as silent as the bouncing of a bubble on velvet.
No explosion, however huge, can transmit sound in the emptiness of the
void.

The magnificent, horrible blast broke into a million gobs and sparks of
molten metal--from what had once been a space ship's hull. Superheated
gas from ignited rocket fuel shot out. Scattered far and wide, the
white-hot fragments of the wreck continued on their way, following
the original direction of the once bold X911 toward Io. Their speed
increased gradually, as the gravity of the Forbidden Moon pulled them.
The larger chunks, falling at meteoric speed, would bury themselves
deep in the cold Ionian deserts.

The secret of Io had claimed another victim, one who might have
been victorious. But Io's mystery was still unviolated. Evan Harwich
had seen other ships, disabled and unmaneuverable for some reason
beforehand, go to their ends like this; but he was still not used to
the spectacle, and to the unholy wonder it provoked in him.

Dazzled and almost blinded, he guided his patrol boat shakily away from
the Forbidden Moon. There was cold sweat in his thick, black hair,
under his leather helmet; and cold sweat too on his narrow, bristly
cheeks. His movements of the controls were a trifle vague and fumbling
with emotion, making his patrol boat waver a little in its course.

For perhaps the millionth time Harwich wondered: "What makes Io so
dangerous? Dammit all, those scientists who claim that there is a
deadly shell of unseen energy completely enveloping the Forbidden
Moon, must be right! There isn't anything else that could explain
the continual destruction of all rocket craft that come within that
five-thousand-mile limit!"

Evan Harwich was ready to accept this much as fact. But beyond this,
there was still a vast, unguessable question mark.

Was this shell of energy a natural phenomenon; or was it something
planned, made, intended for a purpose? If the latter guess was right,
who could have created such a gigantic screen of force? What kind of
beings? What kind of science?

Io was an almost dead world, Harwich knew. Very cold. Very little water
and air. Astronomers had taken photographs of its terrain through
powerful telescopes, from the other moons of Jupiter. Very little could
be seen on those photographs but deserts and grey hills, and curious
formations which might be the magnificent ruins left by an extinct race.

Evan Harwich was far from a weakling; but cold chills were playing over
his big body as he groped to understand the unknown.

His vision was clearing somewhat, after having been so dazzled by the
incandescent blast that had accompanied the destruction of the X911 a
moment ago.

In the feeble sunlight, so far out here in the void, Harwich saw a
second rocket, leaving the scene of the disaster along with himself.
Evidently someone else had witnessed that weird demonstration of Io's
destructive might, too!

Squinting through a pair of binoculars, Harwich read the obviously
ancient craft's number. Then he snapped on his radio again.

"Calling space ship RQ257!" he grated into the transmitter.
"Interplanetary Patrol just behind you. Pilot, please identify
yourself! Do you know who was aboard the experimental rocket X911, that
was just destroyed?"

A few seconds later he heard a dazed, grief-anguished voice speaking in
response: "Yes ... I ought to know. I came out to watch our test of the
Energy Barrage Penetrator, which we thought would be successful. I am
Paul Arnold. The man who was just killed was John Arnold, my father."

John Arnold! Yes, Harwich had often seen photographs of this daring,
hawk-faced old student of the Forbidden Moon in the scientific
journals. He had been the greatest of them all! But there wasn't much
to do for him now but shrug ironically, and report the nature of his
death by radio to the Interplanetary Patrol Base on Ganymede, largest
of Jupiter's satellites.

"I'm sorry, Paul Arnold," the patrol man told his informant in sincere
sympathy.

"Thank you," the quavering voice of Paul Arnold returned. "And now, if
you don't mind, I've got to get back to Ganymede City. Dad's gone, but
I've got to carry on his work."

       *       *       *       *       *

Harwich didn't meet Paul Arnold, the son of the dead scientist, face
to face for more than a month, Earthtime. But on patrol duty out
there in the lonely reaches of the void, with the stars and the roar
of his rocket motors for company, he saw a good deal of the leering,
greyish sphere of Io. It seemed to taunt him with its masked secrets,
hanging so near to the tremendously greater bulk of Jupiter. But the
Forbidden Moon told him nothing new at all. Through his binoculars he
saw the deserts and hills and those supposed ruins. Near the equator
was something that looked like a vast, pointed tower. But Harwich had
seen this before, often. Something moved near the tower now and then,
as on other occasions. But maybe this distant movement was only the
shifting of clouds of dust, blown by a thin, frigid wind, in a tenuous
atmosphere.

Then, back in Ganymede City, came that meeting with Paul Arnold. It
happened at the Spacemen's Haven. Evan Harwich, on furlough now, was
sipping Martian _kasarki_ at the bar.

Presently a hand was laid on his arm. He turned to face a slight-built
youngster, who could not have been more than eightteen. But his
peculiar gold-flecked eyes were as distant and scared and bright as if
they had seen Hell itself.

"You're Harwich," said the boy. "I'm Arnold. They pointed you out to me
as the patrol pilot who reported my father's death. I wanted to talk to
you. I don't know just why, except that you were there too, when Dad
was killed. You saw what happened. And people have told me that you
were a square shooter, Harwich."

Somewhat startled, but glad to know the youth, and more than willing
to talk with him on the subject mentioned, Evan Harwich tried to smile
encouragingly. It wasn't too easy, considering his weathered, space
darkened features and threatening size; but he did his best.

"Pleased to meet yuh, Arnold," he said rather clumsily, offering a big
hamlike hand. "I wanted to talk to you too. How about a drink and a
quiet corner, where the crowd here won't be stepping all over us?"

They retired to a table in a screened nook. "Now," said young Arnold,
"you've seen as much of the Forbidden Moon as anybody alive, Harwich.
You must know that the energy aura around her is real and not a fable.
You must know, too, that it couldn't be a natural phenomenon, since
nothing in nature acts like it does. There's only one alternative
possibility as to what could cause it! Even though Io seems so
deserted, somehow there are machines there, functioning to maintain
that shell of force! Right?"

Harwich nodded. Little glints of intense interest seemed to show in his
eyes. "I've believed that for a long time," he admitted. "But those
machines must be plenty wonderful to build up a barrage of invisible
energy, thousands of miles in extent! Our scientists couldn't even
begin to dream of doing anything like it! Even the principles employed
must be a million years ahead of our time!"

"Right again!" the boy responded. For a second he cast a guarded,
suspicious glance around the room, where Earthmen and leathery Martians
were talking and laughing and drinking.

"The evidence can't be disputed," Paul Arnold whispered at last.
"It might be that the people who invented those machines have been
extinct for ages. But the mechanisms they created are still operating.
There's superscience there on Io, Harwich! How much could we benefit
civilization, if we could somehow find out what the principles of
those machines are? How much damage might be done if those principles
happened to fall into the wrong hands, among men? War and conquest--a
whole solar system thrown into chaos--might result!"

Evan Harwich wanted to laugh scornfully, wanted to call the kid a
dreamer of wild dreams; but the realization that young Arnold probably
told the truth, made his hide tingle and pucker instead.

"Maybe you're right, fella," he growled.

"Of course I am!" Arnold almost snapped. "My father believed it
for years, and his work must go on, even though the Forbidden Moon
scares me plenty. You saw yourself, Harwich, that his Energy Barrage
Penetrator was almost successful. I've been trying to build another,
with enough power to get through."

Harwich's lips curved, a nameless, wild thrill stirring in his blood.
But after all, even before he'd left a great consolidated farm in
southern Illinois nine years ago, to become a spaceman, he'd been an
adventurer at heart.

"Do you suppose you'll need any help?" he asked simply, realizing that
even as he spoke, death on a tomb-world might well be lurking in the
background.

The question sounded like impulse, but it wasn't. Harwich had lived too
long in the shadow of the Forbidden Moon's taunting enigma, not to want
to take a personal part in any effort to penetrate its grim secrets.
Besides, he had a month's furlough from patrol duty now. The thought of
possible adventures to come made his nerves tingle.

Paul Arnold's eyes widened. "I almost hoped you would want to join me,
Harwich," he stammered happily, seeming only to need the moral support
of an experienced spaceman, to bring him out of the black mood he was
in. "Shall we go to my laboratory?"

       *       *       *       *       *

The Arnold lab and dwelling proved to be one of the oddest that Evan
Harwich had ever seen. It was just outside the great steel-ribbed
airdrome that confined a warm, breatheable atmosphere over Ganymede
City, the small mining metropolis of a dying world.

The Arnold lab was a group of subterranean rooms, beneath the desert.
They were reached by a private tunnel from the City, and were
hermetically sealed against leakage of air to the cold semi-vacuum of
the Ganymedean atmosphere above.

Cellar rooms, vaults, not exactly modern but restored from some ancient
ruin; for Ganymede had had its extinct clans of quasihuman people too,
ages ago. A weird place, this was, a place of poverty, perhaps, since
all of the Arnold resources must have gone into experimentation; but a
homey sort of place, too, with its scatterings of books and quaint art
objects and pictures.

"This is the Energy Barrage Penetrator, Harwich," Paul Arnold was
saying in husky tones, as the two men bent over a copper helix or
spiral, attached to a maze of wires, tubes, and power-packs. "I
rebuilt it here on this test-block from Dad's plans; with certain
rearrangements, of course. But we need a new Gyon condenser, if we
want to raise the Penetrator's strength enough to make our venture
successful."

Evan Harwich nodded beneath the single illuminator bulb that glowed
here, its rays glinting from the battered, patched hull of the space
ship, RQ257, that stood in the center of the great room, under the
airtight exit doors provided for it in the ceiling.

"So I see," Harwich commented with subdued eagerness. "Well, that's not
so bad. I can buy a new Gyon condenser from one of the supply shops
in town. I'm no scientist, fella, but they give us a pretty complete
scientific training in the patrol service. Enough so that I can see
that the Penetrator is going to do the trick, this time, with your
improvements. And I don't think it will take very long to get things
ready for a real trip to the Forbidden Moon."

The patrol man had hardly finished speaking, when a door, somewhere,
groaned on its hinges. In the dusty silence there were footsteps,
coming nearer through the series of rooms.

"Well, have we got company?" a voice boomed heavily after a moment.

Evan Harwich turned about slowly. Standing in the arched entrance of
the laboratory chamber, beneath the ancient, grinning gargoyle of
carven granite that formed the keystone of the arch, were two people.
They must have just come in from town.

One was a man, as tall as Harwich himself, but much broader. He looked
jovial, overfed, and just faintly sly. Harwich knew him a little.
He kept a small printer's establishment in Ganymede City, repaired
delicate instruments, and made loans on the side.

"Hello, Harwich!" the big man greeted loudly. "You look surprised to
see me here! Well, I'm just as up in the air as you are, to find you
around. How come? You see I've been financing Paul Arnold's researches
since old John was killed. Has Paulie talked you into some part in the
great miracle hunt on Io, too?"

"Hello yourself, Bayley," the patrol man returned in not too friendly
a tone. "Yes, I've joined up."

Harwich was a little more than surprised to see the fat printer here.
He didn't like the setup at all. Not that he had anything definite
against George Bayley. The latter had always seemed good-natured and
honest, except for some elusive trace of insincerity in his manner, his
voice, and his little squinted eyes.

Was this the kind of man for Paul Arnold to choose as a patron,
particularly when he was in pursuit of the incredibly advanced science
which must exist on Io? A science that might benefit the human race
immeasurably, or might result in wholesale destruction and confusion,
if it was wrongly and selfishly used?

Evan Harwich couldn't have answered yes or no to this question.

       *       *       *       *       *

There was a painful pause in the conversation. Harwich found himself
looking at the girl, who had entered with the big printer, and to whose
arms the latter clung with a kind of bearish possessiveness. She was
small and dainty. Her blonde hair, combed back tightly, fitted her head
like a cap. She was wearing a plain but tasteful black dress with a
white collar.

"Oh, I'm sorry!" Paul Arnold exclaimed after a moment. "Clara, this is
Evan Harwich of the Patrol. Evan, this is my sister. I didn't tell you
that I had a sister, did I?"

The girl only nodded slightly, and smiled a warm, friendly little
smile. But why did the big patrol pilot find her more attractive than
any other girl he had ever seen? Perhaps mostly it was those wistful
eyes of hers, not gold flecked like her brother's, but clouded amber.
They were mild and troubled and knowing. Maybe Clara Arnold's life, as
the daughter of a martyred scientist, had made them like that. Harwich
knew that he might conquer not only the Forbidden Moon, but the stars
themselves, and still remember those eyes.

"Now we all know each other," Bayley boomed. "We're one big happy
family--or are we?" He looked at Harwich significantly, a definite
scowl now crinkling his heavy brows. "Harwich," he added, "we
appreciate your company a lot. Only we are engaged in some pretty
serious business here, and it doesn't allow us to take in outsiders."

For reasons of his own, Bayley was trying to get rid of the big patrol
pilot. But Harwich was inclined to be very stubborn, naturally, and
faint, pleading looks from both Clara and Paul Arnold, made him doubly
so, just at present.

Harwich had the aspect of a very dangerous adversary in a physical
encounter; his weathered features were far from beautiful, and at
certain times he had a way of grinning that made him look like a
good-natured devil with a hot pitchfork hid behind his back. He turned
on that grin, now.

"What's in that package sticking out of your coat-pocket, George?" he
asked the fat printer breezily. "It's about the right size and shape
to be the new Gyon condenser we need. I was going to buy one myself;
but seeing that you've already done so, we might as well go to work
installing it in the Penetrator apparatus."

"Well, all right, Harwich," Bayley growled with some slight show of
timidity. "As long as you're Paul's friend, I suppose you can stick
around."

"Thanks a lot, George," Harwich chuckled, as the printer set the
package containing the precious Gyon condenser on a work table.

The patrol pilot was almost sure he heard faint sighs of relief from
the two Arnolds, as Bayley backed down. Had they come to mistrust him
too, since he had been financing them? Did they feel more at ease
because he, Evan Harwich, whom Bayley could never bulldoze, was their
partner now too?

The spaceman wondered, and he couldn't help wondering something
else. On Clara Arnold's left hand, there was a diamond gleaming. An
engagement ring. Bayley's? The way the latter had clung to the girl's
arm, it couldn't very well be anybody else's. Could Clara, quiet and
beautiful, ever love the boisterous, paunchy printer?

The Arnolds were a strange family, anyway. The son was ready to
sacrifice his life in an effort to reach the Forbidden Moon, where his
father's ashes lay entombed. The daughter? Might she not be of the same
fanatical breed? Might she not be willing to marry Bayley, so that he
would supply funds for their experiments?

For a moment, Evan Harwich felt a sharp, hurt ache, deep in his heart.
But he fought it down. All this was none of his business. And from a
heavy-glazed window slit in the ceiling of the laboratory room, a shaft
of soft light from ugly Io, the Forbidden Moon, was stabbing down,
appealing to his own adventurous nature.

Paul had slipped on a pair of lab coveralls. He tossed another pair
to the patrol pilot. "Come on! Let's get started, Evan," he urged
pleasantly. "We've got a big job in front of us, and remember you said
we'd get through with it before long!"

       *       *       *       *       *

True to Harwich's predictions, the rearrangement of the Energy Barrage
Penetrator for far greater power than the original had possessed, did
not take really a lot of time.

Within forty hours after the patrol pilot's arrival at the lab, the
task of installing the Arnold apparatus in the old space ship, RQ257,
was complete. The tests of the Penetrator had been made, and judged as
successful as anyone could have hoped for.

The space ship stood ready there in the laboratory room, a slender,
copper helix wrapped around its hull.

"All set, eh?" George Bayley boomed jovially. "Got your emergency
supply-packs loaded aboard, too, eh? But you won't need them, boys,"
he added seriously. "You've got everything in your favor. And in five
hours you'll be back here with Clara and me, at the lab with a dandy
story to tell."

Bayley seemed honest and sincere, now. Evan Harwich almost felt
sheepish about the matter. Maybe he'd misjudged the big, bearish
printer. Anyway, he watched his every move, during the assembly and
installation of the Penetrator.

Paul Arnold was whistling a little tune of confidence and exultation.
Harwich's pulses beat happily, his thoughts on the enigma of the
Forbidden Moon, that now must yield to the new Energy Barrage
Penetrator. Superscience there on Io! Unutterable wonders! Who could
guess beforehand what the Forbidden Moon's vast screen of force was
meant to bar from intrusion? But maybe they would soon know!

Only Clara Arnold showed worry. There was a slight shadow in her amber
eyes, when she took Harwich's hand.

"I suppose this is only a preliminary test flight to Io and back," she
said. "Not much dangerous exploration. But please be careful," she
pleaded. "Please be careful, Evan."

The spaceman muttered a word of thanks. Evan. His first name. To have
Clara Arnold use it like that might have given a new meaning to life.
His heart was suddenly pounding very hard, before he remembered that
diamond on her left hand. She was promised to George Bayley.

The girl and the printer retreated from the laboratory chamber, waving
a farewell. The space ship was sealed. The great exit doors in the
ceiling of the lab opened wide, and the air rushed out.

In another moment the RQ257 was shooting skyward. In the night, among
the welter of stars, huge Jupiter and his many satellites shone down on
the Ganymedean deserts. The nose of the ship swung unerringly toward Io.

       *       *       *       *       *

The RQ257, wrapped in its protecting halo of blue fire from the
Penetrator, struck the Forbidden Moon's tremendous, invisible envelope
of energy, squarely. There was a snarling sound in the ship's interior.
White sparks lanced through cold space beyond the windows of the
cabin, as two opposed forces fought each other. But the RQ257 bored on
steadily.

"We're going to make it, Paul!" Harwich shouted through the reeking,
dinning cabin.

"Of course we are!" young Arnold yelled back at him. "How could we
fail!"

The two men were on the brink of success.

Then there was an abrupt, strident, angry, snap from the vitals of
the Penetrator apparatus. Everything seemed to happen at once. The
protecting blue aura outside the ship waxed and waned perilously. And
whenever it waned, there was a grinding, crumpling sound, as of steel
plating being crushed like so much paper in a giant's grip. Heat, and
the cindery pungence of scorched metal, filled the cabin.

Paul Arnold and Evan Harwich were frozen rigid with stunning, agonized
paralysis, as strange energy snapped into their bodies. In the jolting,
erratic motion of the wounded space ship, the two men were hurled from
their feet like a pair of stiff wooden dolls.

Rolling and tumbling, his vision half blinded, Harwich saw the metal
walls of the cabin buckle and redden with heat, as the craft floundered
in that region of mysterious force and energy that heretofore had
destroyed every ship that had attempted to reach Io.

There was another growl from the protecting apparatus. In a flash
of electricity, the side of the bakelite case that housed the Gyon
condenser exploded outward. At once the staggering Penetrator quit
completely. Its last shred of protecting force was gone.

But that momentary hell had ended, too, with almost dazing suddenness.
The grinding, snapping sounds had ceased. And there was only the heat
and the stench of burnt metal, and the weightless sensation of free
fall. That and the mocking stars.

Paul Arnold, panting, his face darkened and beaded with perspiration,
clutched a bakelite handrail in one corner.

"We got through Io's energy barrage!" he shouted wildly. "We did that
much, at least; and for a moment, when our Penetrator went wrong, I
didn't think our luck would be even that good."

Evan Harwich leered back at the youth, from near the now useless
apparatus that John Arnold had invented. "Yes, we got through," he
grunted hoarsely. "The energy shell must be only a couple of thousand
miles thick, with free space underneath, between it and Io itself. The
Gyon condenser kept working raggedly just long enough to get us out of
the danger zone, without being completely blown apart!"

Harwich didn't have to test the controls of the ship to know that they
were useless, now. The rockets were silent too. The RQ257 was falling
free toward the Forbidden Moon, still a couple of thousand miles
beneath.

"But dammit, Evan!" young Arnold growled. "The Gyon condenser
shouldn't have quit on us at all! Those things are tested for heavy
loads of power!"

The patrol pilot was well aware of that. Clinging to the base of the
Penetrator, he was close enough to see detail. The lights in the cabin
had gone out, but the ugly effulgence of Io was streaming through the
windows.

Projecting from the shattered bakelite box of the Gyon condenser, were
two slender, bent wires that should have been joined together. It had
been one wire once, but it had snapped in the middle.

The ends were faintly scorched and blued; but there was something else,
too. They were bevelled off curiously, as if they had been notched.

"Cut with a file!" Harwich fairly snarled. "The wire was cut with a
file. Then the insulation was rewrapped carefully so that all the
evidence was hidden!"

The cause of the accident was plain. The wire had been able to carry
the load of power easily enough during the tests; but under the
additional load of fighting the Ionian hell-zone, it had burned through
and snapped!

"Bayley!" Paul Arnold whispered in the ominous stillness that now
pervaded the plummeting derelict of the RQ257. "He brought the
condenser, you remember! Evan, I know you were careful to watch
everything he did during the assembly and tests in the lab itself. He
must have had the Gyon condenser at his apartment before he brought it
to us. He must have doctored it there! He was planning even then to get
rid of me! And when he found you around, he decided that he wouldn't
weep if he got rid of you too!"

"But why?" Harwich growled in momentary confusion. "Why should Bayley
want to get rid of you?"

       *       *       *       *       *

It was almost a silly question, as Harwich realized at once; but now
Paul was answering it.

"It's simple," said the youth. "Bayley financed me after Dad was
killed--yes. He watched my experiments and tests and studied my
apparatus. He has a pretty keen mind. With me out of the way, no one
but himself will know just how the Penetrator works! He can fix up
another ship and come to Io himself without any competition! Anything
he learns or discovers on the Forbidden Moon will be his alone! Or so
he thinks, anyway."

It was too clear now! Evan Harwich knew that he and the boy were
tumbling helplessly into the maw of hell now. In a useless, derelict
ship they were falling toward the Forbidden Moon! They were already
within the gates of unholy mystery! Death seemed very close. Yet the
cold anger that hissed in the patrol pilot's brain, made him determined
to live, somehow, for revenge!

"We'll be smashed if we stay in the ship, Paul," he said fiercely. "So
we've got to jump for it with our safety equipment."

Quickly and more smoothly than did the youth, for he was well-trained,
Harwich got into his space armor. Next he donned two massive packs, one
on his chest and one on his back.

The exit door of the cabin was jammed, but with his pistol the patrol
pilot fired an explosive bullet into its hinges.

A second afterward, Arnold and Harwich crept through the rent, while
escaping air puffed out around them. They leaped into the emptiness
almost together. With the heat-warped wreck of the gallant old RQ257
falling beside them, they continued their plummeting descent. There
were still almost a thousand miles to go, for the distance between
Io itself, and the gigantic energy envelope that surrounded it, was
perhaps three thousand miles.

Down and down, with only regulation spacemen's emergency equipment to
rely on to avert being crushed on those greyish hills and deserts,
rushing nearer and nearer. Even a thousand miles did not take many
moments at that terrific speed.

The Forbidden Moon was like a sullen, silent nether world, with an
atmosphere so rare that an unprotected human being would gasp and die
in it in a few minutes! Even a man in a space suit could not hope to
survive that desolation for long! Io seemed like a Pit now to Evan
Harwich, an Abyss of Hell from which there was no escape! A place where
no Earth being was meant to venture!

This moment was too grim to think of thrills. Helplessness removed that
intriguing glamor utterly. And there was only savage determination
left. That and smoldering hate of the man who had caused misfortune!

Presently, through the thin metal of his oxygen helmet, Harwich heard
a soft, hissing, whistling sound. Gradually it grew stronger. The
patrol pilot knew what it was, of course. He had entered the intensely
thin upper atmosphere of Io, and the hissing was made by his own space
armored body passing through those tenuous gases at fearful velocity.

The sound served as a signal for action. Again, though the situation
was new to him, Harwich's training made his responses accurate. With
a gauntletted hand, he groped for the metal ring on the pack that
bulged from his chest. It was ancient history when he jerked that ring,
but sometimes, in emergency landings like this, on worlds that had a
blanket of air, however slight, it was still useful. In another second
the patrol pilot was dangling beneath a gigantic mushroom of metal
fabric. He felt the firm tug of the shrouds. Deceleration.

He wondered vaguely why the fragile parachute did not tear apart in the
terrific speed of his fall. But it was the utter thinness of the air,
of course, here in the upper layer. Its resistance was so very slight.
So there was time for velocity to be checked gradually, as the air grew
denser, and its retarding effect greater with lowered altitude.

Paul Arnold had opened his chute too. Its vast top, a hundred feet in
diameter, gleamed dully in the faint sunshine.

In a great plume of dust far below, the derelict space ship crashed.
Fire flew as the force of the impact generated heat. But the wreckage
was out of sight, and there was only a pit smoldering on a bleak, dusty
hillside. The RQ257 was buried deep.

       *       *       *       *       *

Harwich and Paul Arnold landed several miles away from the grave of the
ruined ship; for they had drifted with the thin, dry, frigid wind.

Their booted feet spanged painfully against the sand and broken rock,
and they crumpled to their knees; for even in the feeble gravity of Io
the impact had been heavy.

Harwich snapped on his helmet radio-phone. Young Arnold's voice was
already audible in it, faint and thready and sarcastic.

"Well, here we are, Evan," he was saying. "The first Earthmen to set
foot alive on the Enchanted World! I guess I got part of what I wanted
anyway, didn't I? But with what equipment we've got to keep alive with,
we might just as well be buried with the RQ257! Funny I'm not scared. I
guess I don't realize...."

His bitterly humorous tone faded away in vague awe.

Still lying prone the two men, looked around them, at the hellish,
utterly desolate scene. The hills brooded there under the blue-black
sky and tenuous, heatless sunshine. A rock loomed up from a heap of
sand. It was a weathered monolith with weird carvings on it, resembling
closely those left by the extinct peoples of Ganymede, that other, now
colonized moon of Jupiter. A curious pulpy shrub, ugly and weird, grew
beside the monolith. A scanty breath of breeze stirred up a little
ripple of dust.

That and the stillness. The stillness of a tomb. Harwich could hear
the muted rustle of the pulses in his head. Everything here seemed to
emphasize the plain facts. The Forbidden Moon was a trap to them now.
A pit from which they could expect no rescue. An abyss that was worse
than the worst dungeon--worse than being literally buried alive!

It was like the end of things. Was this the kind of slow, creeping,
maddening death that George Bayley, the treacherous printer, had
planned for them?

Again fury steadied Evan Harwich's determination. Grimly he struggled
to steady his nerves.

"Listen, Paul," he said quietly into his phones. "We mustn't ever let
ourselves think we're licked! That's sure poison! The stuff we've
got in our emergency packs will enable us to keep living for a while
anyhow. We know Bayley'll come to Io sometime, with a ship fitted out
with a new Penetrator. We know he'll be looking for the secret of the
force aura of the Forbidden Moon, and whatever else there is to find.
Maybe we can get ahead of him yet, if we keep on the move. Which way do
you suppose would be best to go?"

Harwich asked this question because Paul Arnold, in his more academic
study of Io, should know more about its terrain than he.

"You know the Tower?" Paul Arnold questioned. "The queer pinnacle, or
ruin, or building, near the equator, on what is known as the Western
Hemisphere? You must have seen it often when you were on patrol."

Harwich nodded. He remembered very well. Only a hundred hours ago,
still on duty as a patrol pilot, he'd seen that pointed mystery from
the void, vague dusty movement around its base.

"It was my Dad's guess that whatever miracles are to be discovered
on Io, they will probably be located around the Tower," Paul Arnold
answered. "But I was careful to notice our position when we landed.
We're far north of the Tower now--a good fifteen hundred miles. A nice,
long walk--especially when the normal air of the Forbidden Moon is too
thin to be breatheable."

"Stop that pessimist stuff, and let's get started!" Harwich snapped.
"We'll have to live very primitively, of course, but who knows what
will turn up?"

They discarded their parachutes and started out, plodding southward,
carrying their heavy packs. As if to save their energy, they did not
speak much.

The hills rolled past, under their plodding feet. More fragmentary
ruins appeared, and were left behind. Their boots sank into soft dust,
as they marched on and on. At first their muscles were fresh, but
tiredness came at last. And the miles which lay ahead were all but
undiminished.

The tiny sun sank into the west and the cold increased. Night was
coming.

"We'd better camp," young Arnold suggested wearily.

So they opened their packs, and took out the carefully folded sections
of airtight fabric that composed their tent. It was part of the usual
equipment kept for emergency purposes by those in danger of being
stranded on dead or almost dead worlds. The tent could be hermetically
sealed. Harwich and Arnold set it up carefully and crept inside. Air
was freed from their oxygen flask, and the queer shelter ballooned out
like a bubble.

They could remove their space suits now, and breathe, here in the
tent. They ate sparingly from their concentrated rations. Meanwhile
a little pump and separator unit, driven by a tiny atomic motor, was
busy compressing the thin Ionian air, separating out the excess of
carbon-dioxide and nitrogen it contained, and forcing the oxygen into
the depleted air flasks.

Once in the darkness Paul and Evan were awakened by a strange sound,
eerie in that dead quiet, and very faint because the scant Ionian
atmosphere could not conduct it well. But when they crept to the
flexoglass window of the tent, they saw nothing unusual.

"I guess we're getting jumpy," Paul whispered nervously, his breath
steaming in the cold, frosty air that filled the shelter.

"It looks that way," Evan Harwich returned reassuringly.

But after the boy was asleep again, he crept back to the frosted window
to watch. He knew that there had to be something mighty on Io. The
shell of force that surrounded the evil moon couldn't exist all alone.
There had to be more. Something that lay back of it, went with it.
Something that could easily be very dangerous.

Jupiter, so near to Io, was a gigantic threatening mass in the heavens.
But its light was deceptive. There were so many dense shadows.

Did he see some of the stars near the horizon wink out suddenly, and
then appear again, as though something big and nameless and sinister
had momentarily blocked their light and then passed on? He could not be
sure, and nothing further happened. To save his companion unnecessary
concern, when nothing could be done about the threatening danger
anyway, he decided to keep the incident to himself.

       *       *       *       *       *

Long before the dawn they were once more on the march. How many hours
was the Ionian day? Something over forty. It didn't matter much.

When the daylight finally came, they had slept again, this time in
their space suits, without bothering to set up the tent. Rising to his
feet, Paul Arnold pointed suddenly.

"Look! An ancient road!" he shouted.

It was true. The highway ran there between the hills. A stone ribbon,
covered here and there with drifted sand, which showed that there was
no traffic of any sort now. The ruins along it looked a little less
battered than those which the two men had previously seen, and there
were vast lumps of corroded metal, too. Machinery in a former age.

"The road goes our way," Harwich commented. "We'll follow it."

Hours later, Paul Arnold offered an opinion. "Part of the mystery of Io
is clearing up, Evan," he said. "The ruins around here. They're almost
identical in architecture to the ruins of Ganymede and the other Jovian
satellites. The evidence looks plain. There must have been a single
great civilization once, extending over all the moons of Jupiter."

Harwich, thinking of, and hating George Bayley for his diabolical
treachery, was only half listening.

"Yes?" he questioned.

"Yes," the boy answered. "And look at those dry ditches, and the big,
rusty pumps! The valley here must have been rich, irrigated farmland,
once!"

They were going across a huge bridge, now, made of porcelain blocks.
It was a magnificent structure, magnificently designed according to
intricate principles of engineering.

"What I can't understand is why all this country became deserted,"
Paul offered. "You'd think that people who could build things like
this would never die out! They could conquer any difficulty that might
come up, it would almost seem. Even if their world got old and worn
out. After all, even Earthmen can make almost dead worlds artificially
habitable again with airdromes, and with imported atmosphere and water."

This was another mystery. But it touched Evan Harwich's thoughts only
faintly. Nor did he care very much when later Paul pointed out to him
rich deposits of ore--outcroppings along the road. He'd seen them
himself, and the tunnel mouths, too, of ancient mine workings. There
were many fortunes to be won here, in costly metals, just as on the
other Jovian satellites. But how could this be important, now, with
death dogging their tracks, and so many other things more important,
to be concerned with?

Evan Harwich reserved his determination for what he knew was coming.
The slow wearing down of stamina. Water he and Paul had a little of.
And more could be reclaimed from the thin, dry atmosphere. It collected
in the bottoms of oxygen bottles, when they were pumped full, condensed
by compression. A few precious drops. You could drink it out after each
bottle was emptied of air. Just about enough water to sustain life.

In the matter of food, you had to ration yourself so stringently
that you caught yourself looking with longing eyes at the few,
weird, bulbous shrubs and the scattered lichens, which were the only
vegetation on this dying world. Only you knew that these arid growths
would never be good to eat.

Those long Ionian days passed. One after another. Five, ten, fifteen.
Harwich knew he was losing strength slowly. The inevitable was catching
up with him. But those hard years in the Interplanetary Patrol Service,
and the rigid physical discipline, had made him as tough as steel wire.

With the boy, Paul Arnold, it was not the same. He was very young, and
not too robust. And he was slipping fast.

"What's the matter with me, Evan?" he would grumble. "All this desert
isn't real, is it? We're not on the Forbidden Moon, are we? I'm
dreaming."

"You're just tired out, that's all, fella," Harwich would answer in a
tone that he would try to make reassuring. He would put an arm around
the kid's shoulders, to support his faltering steps.

Big brother stuff.... Paul had plenty of pluck, all right, but there
wasn't much else left in him. He was wearing out, mile by mile,
staggering under his heavy pack.

       *       *       *       *       *

Every resource was reaching its limit, now. Food supplies had dwindled
away to nothing, at last. The little atomic motor that worked the air
compressor and separator unit, was breaking down. It could hardly pump
enough oxygen into the air flasks any more.

But there was nothing to do but keep on the march, anyway, in spite
of handicaps. Evan Harwich felt as though he was going slowly mad.
Brooding thoughts came into his mind constantly.

Clara Arnold. Where was she now? What had happened back there on
Ganymede? What had George Bayley done? When would he come to Io, with
the ship he would surely fit out with a new Penetrator?

What was Clara thinking? What if she knew her brother was alive on the
Forbidden Moon, but slowly dying? What if Bayley told her that maybe
Paul was still alive, adding that he himself was the only person that
might be able to effect a rescue? What if he had finally used this
means, this possibility, to make Clara marry him? She didn't love
Bayley, the fat printer! She couldn't! And he wouldn't even have to
promise to attempt a rescue--only suggest that he might try. Clara must
be half crazy herself, thinking of her brother. After all she'd lost
her father to the Forbidden Moon too.

The thought of demure Clara Arnold in the arms of that bulky,
squint-eyed printer, who had shown his true colors at last, and
proved his diabolical cleverness, fairly strangled Harwich. Maybe he
had no right to harbor such an attitude. After all he hardly knew
Clara. He only knew her haunting beauty and friendly amber eyes, with
quiet wisdom and a little of the martyr in them--like her father,
perhaps. But Harwich couldn't help thinking. It was only by exercising
super-human self-control, that he kept himself from turning into a
raving maniac.

Supporting Paul Arnold's feeble, struggling steps, Harwich watched
the sky like a starved, wounded wolf. Sometimes, in sheer, wild
determination, he longed to claw at that cold, forbidding firmament,
and climb out of that hell-pit of a world into which he had fallen.
He yearned with a savagery beyond words to claw his way up there into
space, to wherever George Bayley might be, and feel the fat throat of
the man who had tampered with the Gyon condenser aboard the RQ257,
squeezed between his hooked fingers.

But the frigid sky and the bleak, dying hills, and the weary miles,
mocked all his hate-born desires. His numbed, aching feet could only
plod on and on in this grave-like desert. Ruins, rusted machinery,
silence, and cold that crept even through the heavy insulation of his
space armor.

Still, he could remember another thing. In the far distance to the
south, was something wonderful and strange. Something that made the
deadly and insidious energy barrier of the Forbidden Moon possible.
Where the Tower loomed on the astronomical photographs of Io.

That night came at last when a streak of silver fire traced its way
across the sky. It couldn't be anything but the flames ejected from the
rockets of an approaching space ship.

Paul Arnold saw it too, turning his haggard face upward. "There he is,
Evan," he croaked into his helmet phones. "Bayley's coming at last."

"I see," Harwich returned softly; his teeth gritted and his lips
curling furiously, behind the transparent front of his space headgear.

They dropped down beside the wall of a ruin, to watch. The ship was
coming straight in, toward Io. At its tremendous altitude, nothing but
its rocket blasts could be seen at first. But then there was a sudden
flare of bluish light. It had struck Io's force barrier, and that blue
glow was the evidence of a Penetrator, functioning. The craft seemed to
slow a little, as its pale, protecting shell of counter-energy fought
back that invisible, guardian screen of the devil moon.

"He got through the force shield," Harwich growled after a moment. "We
knew he would, of course, with his Penetrator operating right. Damn
him!"

There was no more blue fire visible now; but the little silver-tailed
path of rocket flame, showed that the ship was coming in safe and
sound, its propelling jets working steadily.

Among the stars it turned southward toward that deepest enigma of Io.
Toward the unknown scientific wisdom, which lay hidden somewhere near
the Ionian equator.

"He'll get there in a few minutes' time," Paul whispered. "And I guess
we won't get there at all. I'm sorry, Evan, that I got you mixed up
with the Forbidden Moon. Me--I'm just about finished--now."

       *       *       *       *       *

Paul Arnold's voice trailed away. Harwich turned the boy's
glass-covered face up. In the light of monster Jupiter, he could see
that it was blank and relaxed. The eyes were closed. In the quiet rays
of the giant of planets, the youth looked as though death had already
touched him. But there was a little frosty blur on the inside of the
crystalline face-plate of his helmet. It showed that he still breathed.

Tottering a little himself, Harwich picked the boy up, pack and all. He
struggled to put one foot ahead of the other, marching again toward the
south, where the space ship was rapidly receding. Had his strength been
at normal level, his load, bulky though it was, would have been light
in this weak gravity. But Harwich was near the end of his rope, too.
And so he moved on through that beautiful shadow-haunted, frigid night,
where no man was meant to live.

Many times he had to stop and rest. After a short while, the atomic
motor of the air compressor separator unit refused to work any more.
Harwich tried turning the mechanism by hand. But this was slow,
exhausting work.

He watched the luminous dial of the cold-proof wrist-watch, strapped on
the outside of one of his heavy space gantlets. His mind was getting
dimmer. Cold was biting home, savagely. Harwich wanted to see just how
much longer he could keep going. It was eight hours now, since Bayley's
ship had appeared. Slowly more time crept by. His boots trudged in the
desert dust, mechanically. The hands of his watch moved on. One hour
more. Another.

Why didn't he desert the dead weight of Paul Arnold? But you never
deserted somebody who was like a kid brother, did you?

The patrol pilot's breath was coming fast and short, now. The last
of his air was being used up. It was useless to try to replenish the
oxygen flasks with hand power, even though he was suffocating.

Harwich tripped in the dust, and fell sprawling. Jupiter, shining down
upon him, somehow looked like a fat face, tremendously bloated in
size--the face of George Bayley. Harwich cursed, and tried to crawl
toward the south.

Did he hear a sound through his oxygen helmet--a sound loud enough for
the tenuous Ionian atmosphere to transmit? Or was it only the roaring
of the unsteady pulses in his ears? He tried to look ahead, but his
vision was very dim, now, and the light of Jupiter and his moons was so
confusing. The shadows of the rocks and the ruined buildings were so
very black.

But suddenly Harwich squinted. Something _was_ moving toward him,
skimming low over the ground, but not touching it. Something
that glinted wickedly, and showed long, shadowy arms. It was no
hallucination. Evan Harwich was sure of that! Fear came out of that
numb fog into which his brain was settling. It gave him a last, feeble
spurt of strength. He knew that here he must be facing a tiny part of
Io's colossal riddle.

He tried to crawl away from nameless danger, dragging Paul Arnold with
him. He got behind a mass of million-year-old masonry, tufted with
prickly plants.

But the thing that pursued him, easily overcame his weak, instinctive
effort to find concealment. Cold metal claws closed on him. He felt
himself lifted upward, into the night. His mind toppled away into black
nothingness.

       *       *       *       *       *

Somehow, it wasn't the end of life. Harwich began to regain his senses,
slowly. First he heard a distant, muffled clanging. For a long time
before he paid any real attention to the fact, he was aware that
strange warm rays were pouring down upon his body. They seemed to heal
and soothe his aching muscles.

He opened his eyes at last. Startled, he sat up. Around him was the
warm glitter of glass and metal. His space suit was gone. He was in a
crystalline cage, filled with warm, humid air. Odd gadgets, like ray
lamps used in therapy, were fitted to the ceiling. Strange, tropical
vegetation grew in the cage, and water tinkled somewhere.

There was a kind of soothing quiet over the place, except for that
distant clanging. There was a smoothness to everything; a mood of
mechanical refinement and perfection. It was almost hypnotic, somehow.
It dazed and quieted the senses.

Paul Arnold, clad in the slacks and shirt he'd worn under his space
armor, was lying on the floor beside Harwich. He was still unconscious,
but he was breathing evenly. His color was much better than before. The
rays from the roof above were slowly healing his weakened body.

Evan Harwich shook the boy gently. "Wake up, Paul!" he urged. "This
must be it! The center of Power! The place we wanted to find! Some kind
of machine brought us!"

Paul Arnold rubbed his eyes and sat up. Together, Harwich and the boy
looked around through the crystal walls of the cage in which they were
confined.

"There--there's the Tower!" young Arnold stammered at last, pointing.

It glittered in the faint morning sunshine. It was undoubtedly the same
huge pinnacle that astronomers had photographed from the other moons
of Jupiter. Only it was close, now, its details sharp and clear and
real. Around its slender, tapered spire, thousands of feet aloft, the
faintest of frosty aureoles clung; a ghostly light, like the sundogs of
Earthly winter days.

"The Tower must be the source of the Ionian force envelope, Evan!" Paul
Arnold offered after a moment. "That light up there at its top almost
proves it."

Both men were talking vaguely, thinking vaguely, looking around
vaguely. In part this must have been because of sheer wonder. Places
like the Spacemen's Haven on Ganymede seemed as far away as a dream now.

An incomprehensible sense of depression was creeping over Evan Harwich,
as he studied his surroundings further. There were many other cages in
view, arranged in blocks, with paved alleyways between. Vegetation was
thick in the evidently air-conditioned habitations. Little pools of
water glistened in them daintily, strange paradox on dying Io.

And there were creatures, too. Scores of them in each cage. Strange,
fragile, sluglike animals crept about aimlessly. They looked just
faintly human, with their pinkish skins and manlike heads. But there
was no slight shadow of intelligence in those great, sad, stupid eyes.

Harwich wasn't squeamish, but he looked at these futile animals with a
certain pitying revulsion. "What kind of a nursery place have we got
ourselves into, Paul?" he grumbled quizzically.

Arnold shrugged. "They're something like men, these things, aren't
they?" he offered in puzzlement. "Maybe that's another unknown
quantity to figure out. But this place is plenty wonderful, though.
Look!"

The youth was pointing upward. Against the cold Ionian sky a flattened
object was circling at low altitude. A flying machine without wings, it
seemed to be. From it dangled strange webby metal arms, as it moved in
a circular path, above the surrounding desert hills. It seemed to keep
watch over those thousands of crystal cages in the valley. It must be a
guardian of some sort.

"I'm not at all sure I like it here," Harwich growled. "We were fixed
up, revived, made new men again, so to speak; but still I don't like it
here."

"Somehow I've got the same idea," Paul Arnold agreed with a quizzical
smile.

A little clinking noise behind the two men made them turn about. After
that, awe kept them spellbound. They didn't speak. What was there to
say? They didn't try to retreat, either. What was the use? If what
they saw was danger, they could do nothing to avert it. Hypnotized
with wonder, they only stared, feeling as helpless as the larvae in an
ant-hill, tended and cared for by the workers.

       *       *       *       *       *

A section of the cage-bottom had raised, like a trapdoor. A bulk was
creeping through the opening. It was a machine, so marvelous, so
refined in its functioning, that it seemed far more than alive. It was
flat, like a small tractor; but there were no treads for it to move
on. It seemed, rather, to glide on a cushioning, grayish mist. The
thing purred softly, like a great cat, and tiny lights twinkled in
crystalline parts of it--batteries to deliver fearful atomic or cosmic
power, perhaps. The mechanism had many flexible tentacular arms of
metal that glinted with a lavendar luster.

But even the substance of those arms, the metal itself, looked
indefinite and eye-hurting at the edges, as though it was partly
fourth-dimensional, or something.

Both men grasped the truth. Here was that million-year advancement of
science that they'd talked about with such thrilled fascination, in the
stuffy bar of the Spacemen's Haven, back in Ganymede City. But Ganymede
City, with all its human crudeness and inefficiency, seemed like a
lost, happy legend, now, to Arnold and Harwich. Far, far away, and
dim. For here was dread wonder to eclipse it. Futurian fact! Physical
principles of such a miraculous order that mankind had scarcely dreamed
of their outer fringes yet, were functioning here.

The flat machine advanced. But it was only instinct working, when the
two men crouched away from it a little. It was useless to fight; it was
useless to run.

"Get away, you!" Paul Arnold grumbled dully to the mechanism. "Beat it!
Scram."

And Harwich was reacting in a similar manner. "What the hell!" he
stammered. "What are you trying to do with us."

It was almost funny--the ineffectual, confused protest of those two
men. They were like children too lost in their new environment to know
what was dangerous and what was not.

Misty, lavender tentacles reached out and grasped them carefully. They
were lifted from the floor of the cage like babes. Once Harwich's great
freckled arms tautened, as though he was going to battle the monstrous
miracle that held him. But futility checked the urge. Where was there
anything to win by struggling, now? And how could a mere man win
anyway, against soft-moving mechanical power, that should belong to the
far future? Oddly the tentacles were warm and tingling, not cold like
you'd think metal should be.

And so Arnold and Harwich submitted to a paternal, mechanical
dominance, regretfully, because there was nothing else to do. It hurt
their sense of freedom, but where was there any alternative?

Still floating a little off the tile pavement of the cage, the machine
carried the two men easily to the opening in the floor, and glided down
into a crystal-roofed tunnel. There it began to accelerate swiftly,
flying with bullet-like speed, a foot or so above the glass bottom of
the passage.

The tunnel's roof was transparent as air. Through it, Harwich and
Arnold could see that they were nearing the Tower rapidly. After only a
moment of whizzing, breath-taking flight, they had arrived within that
great, enigmatic edifice, for the passage entered its base.

There, in an eerie half-twilight, the flat little machine released the
two humans whom it had brought here, to the Tower.

Mute with an even greater wonder than before, Harwich and Arnold stared
around them. The room was gigantic, soaring up in a huge, metal-ribbed
dome. Scores of crystal-walled passages led into this colossal chamber
of secrets. The whole immense Tower building was transparent, except
that some darkening pigment had been added to the material that
composed it, 'till it was like bluish glass. Through it the desolate
surrounding hills of Io could be seen, and the cages, filled with those
aimless, pathetic, sluglike creatures.

But the attention of the two men was drawn inevitably to the center
of the room. Rearing up there, under the rotunda of the dome, was a
massive, lavender-sheened pyramid. It gave a steady, throbbing sound,
as of countless tiny wheels and shafts whirling inside it, working cams
and rods, and who knew what else?

"Dammit!" Evan Harwich kept muttering under his breath in dim
confusion. "Dammit."

He was used to machinery, yes. He was used to the roar of rockets,
and to the delicate instruments used in space flight. But this was
machinery of a far higher order. That busy, vibrating pyramid,
squatting there like some huge idol, somehow seemed to possess a
definite personality of its own!

Suddenly Paul Arnold clutched the patrol pilot's arm. "I wonder if I
believe what I see!" he whispered tensely. "Look!"

Harwich's gaze followed the lines of the boy's pointing finger to
something quite near--so near, and seemingly so insignificant in this
vast, somber, throbbing interior, that he had not noticed before.

Just at the base of the pyramid there was an artistic little structure,
consisting of four slender pillars and a roof. It looked like a small,
ornamental kiosk or arbor, so artfully were the scientific details of
it--the coils in its top, and the delicate filaments that pronged from
them--concealed in the decorative metal scroll-work.

Within the pillared structure, somehow, there stood a man--an Earthman.
His heavy body was clad now in a rocketeer's leather coverall. At his
waist dangled a heat pistol, and on his fat face there was a strange,
wild sort of smirk.

"Howdy, boys!" he greeted. "Yes, it's me--George Bayley, the guy who
used to keep a print shop in Ganymede City! I've been here longer
than you have, and I've been able to find out more. Pretty nice, huh?
The people of Io had science perfected before they became extinct.
Everything was done by machines, even investing. Not a bit of work to
do any more. And if they wanted anything special, they just came into
this little coop, here, and wished."

       *       *       *       *       *

Bayley paused, still smirking. His loud voice had seemed distant in
that great room, and vibrant with awe. Harwich and Arnold stared at him
for a moment, neither knowing quite what to say, or what to believe.

And what was that which had just spilled from his lips, as though he
had been a little afraid of the statement himself? About perfected
science, and wishing?

"You're crazy!" Evan Harwich stormed fiercely. "You're a liar!"

But his furious tone was tremulous with doubt, even as he spoke. He
knew at once that he'd just grabbed onto these words, and uttered them,
maybe because, somehow, he hated Bayley, and wanted to contradict his
seemingly impossible claims. But in this temple of un-Earthly marvels,
one's whole standard of judgment was upset. Possible and impossible
became meaningless terms here, at the foot of this great, whirring
pyramid, which seemed a symbol of omnipotence.

"Crazy?" Bayley questioned. "No, Harwich, you can't say that, when
you're all tangled up and fuddled yourself! What I said about wishing
is true. Telepathic control of machines, it must be. This place is so
damned wonderful that it would turn Aladdin of the Wonderful Lamp green
with envy! And it would drive the Genie of the Lamp down into his shoes
in shame!"

Harwich's doubts, if they had been doubts, and not just confusions,
began to dim a trifle. After all, one of the big objectives of the
science of Earthmen, was to make life easier; to transfer as much of
the burden of work as possible to machines. Why couldn't the same
objective have been conceived here on the Forbidden Moon? Not only
conceived, but accomplished? Io was an old world; life had begun here
sooner than on Earth, and science, too! So there had been more time for
advancement.

"All right, Bayley," Harwich growled grudgingly. "Tell us what you've
discovered."

"Yes, for Pete sake, tell us!" Paul Arnold joined in.

It was odd, the way they were asking the fat printer for information,
now, when they should be hating him for the wrongs he had done them.
But, perhaps, the human mind can hold only so much at one time. For
the moment there was room only for dazed awe and questioning in their
thoughts, and hatred was temporarily pushed into the background. The
equal of Aladdin's miracles did not seem so far from possibility, here!

"Okay!" George Bayley rumbled. "Glad to spill the beans; what I know
of them. I arrived here in my space ship about fourteen hours ago,
when it was still dark. The Tower building here looked by far the most
important, so I came straight to it. There were machines flying about,
but they paid no attention to me at all, so I wasn't worried much about
what they might do to me.

"Leaving my ship on the other side of the Tower, I got into this room
through a tunnel. I was wearing a space armor, of course. I passed
through a kind of airlock. This chamber was just like you see it now,
except that lights were burning, because it was night."

"And then?" Paul Arnold questioned eagerly.

"Exploring, I climbed into this little metal coop, here at the foot of
the pyramid," Bayley went on. "By then I was pretty flabbergasted with
all I'd seen. I began to think I needed a drink of something strong.
Yep, it must have been telepathy! Because presto--one of those flat
flying machines with the tentacles, whizzed up to me from a tunnel
exit. It was carrying a kind of crystal carafe.

"Boy, I didn't know what to think! I didn't know whether I ought to
taste the stuff in that carafe, at first. But finally I did. It was
damned good. Not alcoholic, but something a whole lot better."

Harwich and Arnold looked at each other, as Bayley paused, as if to get
his breath. They looked up at the pyramid, throbbing above them, like
some great, cryptic, servant personality. The feeling that Bayley was
telling the truth, was growing on them.

"Naturally you tried other things, after the carafe was brought to you,
Bayley," Paul Arnold prompted. "You wanted to see how much further this
expression of desires by telepathy might be carried. You wanted to see
how much more you could use the ancient Ionian science."

Bayley, still standing in that little metal-pillared structure, nodded
slowly. "You catch on quick, Arnold," he said. "First I wished for
gold, since it was the first thing I thought of. The sounds inside the
pyramid changed a little, as though an order was going out somehow,
maybe by radio. Five minutes later a whole bunch of those flying
machines came into the Tower here, carrying bars of gold in their
tentacles. There it is."

The printer was pointing toward a dully gleaming heap of yellow ingots
near the farther wall of the chamber.

"But this, I soon found out, was just kid stuff!" Bayley continued. "I
suppose if I'd thought of radium here in this wishing coop, I would
have got a couple of tons of that, too! But I wished for a space
ship--something special, beyond anything an Earthman ever saw before!
Well, the pyramid buzzed a little longer and stranger this time, as
though it was sort of thinking and planning, and as though the wheels
inside it were maybe inventing, too. Then, somewhere far off, there was
a lot of pounding for about an hour. I guess you know the answer, boys.
There she is--the sweetest little super-futuristic space flier you ever
saw!"

Harwich and Arnold stared at the torpedo-like ship that rested in a
cradle-like support nearby. It was completely without rocket-tubes,
or other visible means of propulsion. But its rakish lines and wicked
lavender glitter made it look as though it might well reach the distant
stars themselves.

       *       *       *       *       *

Evan Harwich bit his lip tensely. Suddenly a thought struck him. "Did
you see any Ionians since you've been here, Bayley?" he asked. "Any
living, intelligent beings who might question your right to be prowling
around?"

Bayley laughed. "Not one!" he returned. "They're extinct, I'm sure of
it! And that's lucky for me."

The patrol pilot was beginning to put the pieces of the Forbidden
Moon's riddle together at last. And Paul Harwich must have been doing
the same. The evidence, as far as it went, was clear.

Perfected science! The fat printer had told them that all you had to do
was think your wishes in that queer little pillared structure. And the
machines translated your wishes into fact. Unless Bayley had lied, and
there was small reason to suppose that he had, the rest was maybe not
so difficult to understand.

First, the great envelope of force around Io. That was to keep
possibly dangerous intruders away, of course. Thus, the ancient
Ionians had lived in carefree idleness and luxury, tended by their
perfected machines. The thing in the pyramid must be the master servant
mechanism, reachable in that pillared kiosk, by telepathy. It must be
the coordinator, in contact with the other mechanisms by radio, or
something. Adding and calculating machines, way back in the Twentieth
Century, had thought and reasoned, after a fashion. More recently, on
Earth, apparati of a similar nature had done far more, working out
intricate mathematical problems, far more swiftly and accurately than
any human being could.

And the apparatus within the pyramid must be much the same thing, but
developed to the nth degree! A vast planning, calculating device that
could reason and invent with a swiftness and perfection far beyond any
living mind. But it was still just mechanical; a servant apparatus that
thought by the turning of the wheels and the movement of levers inside
it with no more consciousness than an adding machine of the Twentieth
Century!

This was the way Harwich figured it all out. And he saw something else,
too.

"Uh-uh, Bayley," he remarked suddenly. "Soon after that new space flier
was brought here at your command, you decided that you were complete
boss around here, didn't you? There were no ancient Ionians in your
way. All you had to do was wish, inside that telepathy kiosk, and it
was just like Aladdin wishing with his lamp, eh?"

For the first time, cold, comprehending anger had come into the patrol
pilot's tone.

"Why sure--sure!" Bayley growled back at him. "And why not? Just about
anything I can think of is possible! And, let me tell you something
else, you poor dope! You and Arnold wouldn't be alive now, if I hadn't
wished it! I thought you might have gotten through the Ionian force
shield somehow, when the RQ257 cracked up. I thought you might be
somewhere out there on the desert still living. So I just wished that
the machines go and get you, and revive you if you needed it. I thought
maybe it might be fun."

It was enough. Cold anger reborn in Evan Harwich's breast was suddenly
rekindled into blazing fury by the memory of the RQ257, and a wire
filed almost through in a Gyon condenser. Evan Harwich's muscles
tightened. Wordlessly he was about to leap at George Bayley.

But a warm metal tentacle whipped suddenly about his waist. The flat
mechanism that had brought him and Arnold to the Tower, had seized him.
Again, he was helpless.

"You see?" Bayley drawled. "I really am boss, here, just as you said.
I just wished that you be restrained, and you are! But I've been doing
too much talking and explaining. How about a little showing for a
change, huh?"

"Damn you, Bayley!" Harwich growled, but the fat printer ignored the
curse.

He only grimaced crookedly. "Let's make a couple more wishes," he
taunted. "A couple of really good ones! How about a whole fleet of
space ships, for instance? The biggest, most powerful fleet in the
solar system! All automatic craft, capable of flying and maneuvering
unmanned! Then, let's see, the other wish? It's not so difficult
either. Both you and Arnold are my deadly enemies, Harwich. I think it
would be fun to make my enemies squirm a little. I'd like to see you
crack up, Harwich! You've always been so tough! So how about some kind
of a discomfort device? Something really special? In short, a torture
instrument! Come on, pretty machines! Do your stuff!"

Paul Arnold's face turned pale, but he bit his lip courageously. Evan
Harwich studied the strange, wild light in the fat printer's squinted
eyes, and waited for whatever would happen.

There was a crescendoing whir within that huge pyramidal coordinator.
The man who had usurped the rule of the ancient Ionians over their
mechanical servitors, had given his telepathic orders. Already there
were signs of obedience. Thinking and planning was going on in that
pyramid; thinking and planning more intricate than that of the greatest
human wizard that had ever lived, more soulless and swift than that of
an adding machine.

Presently, from far away, came a thin, shrill sound. Looking back
through the darkened glass walls of the Tower room, Harwich and Arnold,
both of them clutched, now, by the tentacles of the flat robot, saw a
horde of black specks collecting against the sky in the pale sunlight
outside. A flock of those flat, tentacled, flying things.

They seemed to emerge from an opening in the ground; from a vault where
perhaps they'd been stored for ages. In a gigantic swarm they hovered
over the glass cages and their pathetic animal inhabitants. Then,
drifting like gulls away from this weird city of the Forbidden Moon,
they moved off toward the surrounding hills.

There, like swarming bees, they settled in their tremendous numbers, on
the open, arid valley. Flame tools in their tendrils were brought into
play. Dust, reddened with heat, began to rise.

"They're leveling the ground!" Paul Arnold whispered hoarsely. "They
must be preparing a shipyard!"

"Sure, kid," George Bayley laughed, trying to conceal the half-scared
wonder in his own voice. "Maybe it'll take weeks for them to build the
fleet I asked for! But they'll do it! You'll see, if I happen to let
you live that long!"

       *       *       *       *       *

The unholy wizardry of the Forbidden Moon was proven beyond all doubt.
And in this weird Tower room, air-conditioned against the cold thinness
of the atmosphere beyond its wall, the pyramid still throbbed a shrill
portent of more to come.

A second robot mechanism soared into the chamber from a tunnel mouth.
It bore a curious tripod-like instrument. The flying automaton
spiralled down like a bubble, and came to rest beside Harwich and the
youth. Pinioned by the tendrils of the other automaton, they were
helpless to do anything but watch and submit. They were pushed flat on
their backs, and held firmly. The tripod instrument was set up between
them.

"The discomfort device, this must be!" Bayley gloated, shifting his
weight from one foot to the other. "In just a few seconds there's going
to be some fun, I'll bet! Now, Harwich and Arnold, I'm wishing you bad
luck. Just a little foretaste of what I might wish later! Okay, pretty
machines! Give my beloved enemies the works, just for a second."

Two rods of metal, projecting down from the tripod, were set in
position by one of the automatons. One rod touched Harwich's skull, the
other Paul Arnold's. A switch was moved.

There was no sound; but all of the patrol pilot's body seemed suddenly
and maddeningly afire. To the very center of his mind, agony stabbed,
viciously. No searing pain of any injury he had ever received, could
have equaled this. He writhed, longing to scream his lungs out, as that
moment of sheer hell seemed to last an age.

"God!" Paul gasped when it was over.

Both men were sweating and limp, and yet no visible harm had been done
to their bodies. Artificial sensation, the torture must have been.
Nerve impulses transmitted directly to the brain. A devilish, perverted
achievement of superscience! Such agony might conceivably go on, in
Satanic refinement, for months, without bringing death.

"You see, boys, I'm boss here as long as I stay in this little
telepathy coop, where the old Ionians used to give their orders!"
George Bayley hissed triumphantly. "All the wonders of the Forbidden
Moon are mine to use, just as I see fit! There were just a bunch of
machines here, waiting for somebody to control them. A pistol doesn't
ask who pulls its trigger! And I got here first!"

"I was afraid of something like this when we were still on Ganymede,
before any of us knew," Paul Arnold muttered raggedly.

And Evan Harwich understood very well what the youth meant. George
Bayley was feeling that touch of power here. A sense of omnipotence was
flattering his shallow ego, raising him in his own estimation to the
level of some ruthless god. He, who had been a petty business man, a
printer, a repairer of instruments, a loan shark! Just a crumby, fat
little human being, ridiculous, small and conceited. Pathetic, too,
stubborn, and lacking in judgment. There were many like him on Earth,
and among the scattered spheres of Earth's interplanetary empire.

Maybe, after all, the wisdom of the Forbidden Moon was too big for the
human race. Maybe they would have to grow themselves first, advance in
evolution, before they would know how to handle and how to win real
benefits from such wisdom.

"All right, Nero," Harwich growled contemptuously to Bayley. "I'll
grant that you're in the driver's seat, ready to stop nowhere. Building
a space fleet and all. But where is Clara Arnold?"

The patrol pilot asked the question with fear and doubt in his heart.

"Clara Arnold?" said Bayley almost casually. "Too damned clever for
a girl! Said she thought I might have had something to do with the
crackup of the RQ257. Said she was worried about Paul and you, too,
Harwich, being maybe stranded still alive here on Io. But she said that
she'd finally decided my promises weren't good for anything, anyway.
That I'd have to rescue you two men first before she'd believe in me.
Until then, our engagement was off."

Harwich felt a brief wave of elation, as he heard these words. Clara
had seemed so quiet and timid; but she'd evidently proved herself
plenty courageous and plenty smart.

"But where is she?" Harwich growled angrily. "Now, I mean!"

"Don't get excited," Bayley sneered. "She came to the Forbidden Moon
with me, hoping to see you and the kid again. I left her locked in my
rocket. But she can't mean much to me any more now! Not when they
begin to hear about me all over the solar system! Just a passing fancy!
I suppose I might just as well have the machines bring her here now, to
see just how completely helpless you two dopes are!"

       *       *       *       *       *

Harwich and Paul Arnold were still pinioned to the floor by the
automatons; but in the patrol pilot's slitted eyes glowed the subdued
light of murder, futilely smoldering. The fat printer was absolutely
master now of Clara, the boy, and himself. In his stupid, cruel,
shallow vanity, cosmic power the deeper secrets of which he could
never have understood, had driven Bayley to madness; to megalomania.
That clanging and that red glow from near the distant hills showed the
extent of his ambitions beyond question. The slave machines were not
building that colossal fleet of space warships for nothing! Armed with
weapons beyond human knowledge, such a fleet would sweep in aggressive
fury to even the remotest world within the field of the sun's gravity!

But Harwich's feelings changed briefly to relief, when Clara Arnold
was brought into the Tower room by another of those metal slaves.
The automaton removed from her a flexible, transparent covering, of
evidently airtight material, a protection against the rarity of the
Ionian atmosphere, probably, for in being taken from the airlock of
Bayley's rocket to the air-conditioned Tower here, she would otherwise
have been exposed to suffocation.

The machine set the girl down gently. She looked scared, her blonde
hair was awry, as though, maybe, she'd struggled with the robot; but
otherwise she was still all right.

She looked about in wondering terror; for what she saw was still a
complete mystery to her, just as it had been to her brother and Evan
Harwich a little while ago. No one had told her anything yet.

"Paul--Evan!" she stammered "What is all this here? This pyramid, and
Bayley? What's happened? Tell me, somebody!"

"Take it easy, Clara," Harwich responded, trying to sound reassuring.
"Everything will be all right!" he ended a little unconvincingly,
trying to shield the girl from grim truth.

"Everything's all right already, Clara," Bayley assured her mockingly.
"I've got these two men of yours just where they can do the least harm!
How would you like to see 'em squirm a little? I've got a special
device for that purpose, something very refined and painful! And I've
got just about everything else! In a month's time I could give you the
planet Earth, to wear in a ring around your finger, if I happened to
want to."

"What's he talking about, Evan?" the girl pleaded again, the shadow of
fear in her face deepening. "It sounds sort of awful! Please tell me.
Why are those flat monsters holding you and Paul to the floor?"

"I told you to take it easy, Clara," Harwich returned with a trace of
sternness. "This maniac, Bayley, has got the upper hand now, but I said
everything would be all right, didn't I?"

The patrol pilot was trying again to reassure the girl, with a show
of truculent bravado this time. He hoped that truculence would make
his words sound true, as though he had a trump card up his sleeve, or
something.

"All right in the end, Harwich?" the fat printer chuckled wickedly.
"Well, the end's pretty close. In another minute you'll be too tortured
to do anything but scream. Right now I'm thinking and wishing. Look,
the automatons are getting that agony tripod ready again!"

It was true. Metal tentacles were whipping about, adjusting the torture
rods to touch Harwich's and Paul Arnold's skulls again.

Everything will be all right! That statement was a mocking memory to
the patrol pilot now. An empty, rash challenge to the man whose petty
ego yearned to control even the solar system.

Harwich had never felt so completely helpless in his life before, not
even when he had been suffocating out there on the deserts of the
Forbidden Moon. If he could only somehow knock Bayley out of that
little, pillared structure that served as a receiver for telepathic
orders to the machines; if only he could replace him there for a
second, then everything might be very, very different! But Harwich was
held helpless to the pavement of the tower room. His massive muscles
were useless against machine might!

Direct argument--an attempt to make Bayley see the narrowness and lack
of originality in his colossal ambitions--he knew was equally futile.
Bayley was stubborn and shallow and greedy. Besides, he would never
admit that he was wrong, even if he felt the truth of it!

So Harwich felt utterly checkmated on every side. The clanging out
there, the building of the space fleet, mocked him. The rustle
of wheels in that huge pyramid coordinator mocked him. All the
Aladdin-like miracles of the Forbidden Moon mocked him, pointing out
his impotence to do anything, now.

He even wondered savagely why that great coordinator mechanism, with
all its terrific powers, didn't revolt against the dominance of the
puny human being that mastered it. But, of course, it would have no
desire to revolt. It had no desires of any kind, no capacity for
happiness or misery, no consciousness even. It was no more alive, no
more sentient, than an adding machine. Only infinitely more complex. It
invented things and it directed lesser mechanisms only by the rolling
of the wheels and the surge of energy inside it. And it responded to
telepathic control of whomever was there to give it, just as a space
ship might respond to whomever was at its throttle.

Still, there had to be some way out of this mess! Harwich knew it
wasn't just Clara and Paul and himself that were in danger. It was
everything he knew and respected. Freedom. Liberty. Unless he and his
companions were able to do something, a Dark Age would come, surely. An
age of machines, ruled by a madman.

The rod of the torture instrument was touching his skull. In just
another moment the agony would begin. But what was Paul Arnold
muttering beside him?

"Evan, those animals in the cages! We thought they looked like men
didn't we? Here's something else: Maybe they are men, in a way! Men who
went backward in evolution; lost their intelligence."

       *       *       *       *       *

No one but Harwich could have heard the boy, for he spoke in a very
low tone. But at once the patrol pilot understood; grasped a part of
the Ionian riddle that he had missed before. Machines. No thinking or
work to do. Indolence. And then?

At once Harwich saw a way, a slim possibility to avert cosmic
catastrophe. He couldn't appeal to Bayley's reason, but maybe he could
appeal to his fears. He had to try it, anyway.

Suddenly the patrol pilot's lips curled in derision and contempt.
"Bayley," he said, "you're an utter damned fool! You think you'll
extend your power all over the solar system. Well, maybe you will do
that; but in the end you'll be destroyed! You give the orders--sure!
But do you understand the thing in that pyramid? It was made to serve,
as all machines are. The ancient Ionians had it pretty nice for
themselves, yes. But did you ever wonder what happened to them? _Where
are they now? Do you know, Bayley?_"

Harwich's final question was a dry whisper, like the voice of some
ghost of ages past.

"_Where are those ancient Ionians now, Bayley?_" he repeated.

No man could have escaped awe there in that tremendous Tower room,
where all the mysteries of the eons seemed to be congregated, many of
them hidden and unknown and perhaps dangerous. George Bayley's eyes
were suddenly very big. Quite evidently there were many things that
he had not thought about. His gaze lingered momentarily on the great
throbbing pyramid, inscrutable there in this huge dusky chamber.

"Stop trying to bluff me, you crazy idiot!" the fat printer stormed at
last. "The Ionians are extinct, of course!"

Harwich managed to grin wolfishly. "If you believe that, Bayley, do
you want to follow them into extinction?" he questioned. "Yes, they
mastered science. They conquered even the problem of the thinning
atmosphere and the loss of moisture and heat on their dying world.
But after they turned their science over to the machines, something
happened to them. Their numbers began to grow less, yes. They lost
control of their empire, which must have included all the moons
of--Jupiter. But they didn't completely die out, Bayley! Something
happened to those Ionians that was far worse! Do you know what it was,
Bayley? Do you want the same thing to happen to you?"

"I don't know what you're talking about!" the printer stammered
furiously, fear of the unknown spreading over his plump face.

"No, those ancient people of the Forbidden Moon didn't become
completely extinct," Harwich continued. "I believe you can see quite a
few of them from the Tower room here. The walls are semi-transparent,
and those cages outside aren't far away. They're full of Ionians.
Sluglike, brainless monstrosities without even intelligence enough or
will enough to wish any more!"

Harwich paused to let the facts sink into George Bayley's mind.

"That's them!" the patrol pilot continued. "It's an old theory that
any race has to keep struggling, thinking, working; otherwise it goes
backwards. By using their brains and muscles, Earthmen developed from
apish ancestors, you know. But here the Ionians had everything done
for them. So evolution was reversed. They lost their intelligence. And
now, what are they? Stupid beasts, tended by machines that follow the
original orders of long ago to take care of them. Worse than animals in
a zoo."

Bayley's eyes were fairly popping, as he stared through the
semi-transparent walls of the Tower room. Doubtless he could see
those creatures in their air-conditioned habitations. Just helpless,
squirming, incubator freaks!

"I wondered what they were--why they were here," Bayley stammered.

Harwich almost believed at first that he had won a point with the obese
loan shark--scared him out of most of his wild ambitions. But then,
gradually, he saw Bayley's expression grow a trifle less tense. It was
just as Harwich had feared. The printer was beginning to realize that
it must have taken countless generations to degenerate to their present
sorry state. The same condition could not affect him personally. When
Bayley saw this truth, he would be the same megalomaniac as before.

There was only that one slim chance left for Harwich. Bayley's
attention was strongly diverted now. But in a few seconds more, he
would be himself again.

Was the grip of the metal tentacles that held Harwich a little looser
than before, now, because Bayley, the master of machines, had his mind
so intensely on other things, and away from the thought of giving
telepathic commands?

In a sudden, savage lunge, Harwich jerked free from the automaton that
held him to the floor. His clothing was torn and his flesh scraped, but
what did this matter? Everything depended on instant action. The patrol
pilot leaped past Paul Arnold, and his sister, Clara, who had only
watched and listened while he had talked with such grim truth to Bayley.

       *       *       *       *       *

Already the flat, glittering robot was after Harwich, but he continued
his surprise rush toward the roofed, pillared kiosk that was the
receiver for telepathic orders.

His attack ended in a dying tackle. Bayley was drawing his heat pistol,
but before he could fire it, Harwich's weight struck him. There,
together, in the kiosk, they wrestled and fought. At last there was a
chance for the patrol pilot to bring his massive muscles into play.
He swung his heavy fists, and all the fury of weeks of hardship and
misfortune were back of his blows. Bayley tottered away from under the
kiosk, and for a second Harwich stood there free.

He was in the position of control at last; but Bayley had his pistol
out and aimed, now. Clara was screaming as the fat man pressed the
trigger.

It was too late for Harwich to marshal his thoughts properly. He was
only able to will that the automaton behind him should cease attacking
him. He could not call to his aid any of the great science of Io, in
time.

With the speed of light, a slender pencil of intense heat waves from
Bayley's pistol, struck his side and burned straight through his body.
No bullet could have drilled a neater hole. Harwich's legs collapsed
under him, and he lay writhing there within the kiosk.

A split second later the heat pistol in Bayley's hand spat again.
Turning weakly, Harwich saw Clara crumple and go down. In another
instant, Paul became the third victim.

"You're done, Harwich!" the fat printer was yelling triumphantly.
"You're finished, all of you!"

But by now the patrol man's seething flood of hate had registered.
He was within the telepathy kiosk; and if he had ever willed instant
destruction for anyone, he willed it now, for Bayley. Under other
circumstances he might not have felt so vengeful, but his ebbing pulses
blazed with fury.

There was a click within that vast, slumberous pyramid, that loomed
like a grim god in this shadowy place of enigmas. The automaton that
had recently held Harwich captive, seemed to move like a maddened
animal, created out of pure lightning. Its tentacles whipped around
Bayley long before he could fire again. Harder than steel cable, the
tendrils tightened, like the coils of a python.

There was a choked cry of terror and anguish, and then a sickening,
crunching, squashing sound, as flesh and bone and blood oozed between
those constricting metal loops.

It was almost the last thing that Evan Harwich saw. He was mortally
wounded, a slender hole bored through his side.

Harwich's last delirium was a dream. A silly dream, maybe. Clara and
he together. A little house. Fancifully he pictured its details. Maybe
a mining concession somewhere here among the moons of Jupiter, too. An
orderly life. Not all this hectic battling with unknown dangers any
more. He was a little tired of adventure, a little tired of being space
patrol pilot, too. He could resign.

Somewhere, Evan Harwich's fanciful thinking came to an end.

       *       *       *       *       *

He awoke suddenly. Paul Arnold was shaking him.

"On your feet, you big lug!" the boy was yelling happily. "There's not
a thing wrong with you, now! Clara and I have been awake for half an
hour."

Harwich staggered erect, grumbling confusedly, his stiff, black hair
awry. He'd been lying on a divan. The room around him was almost
familiarly furnished, except for slightly fantastic details of
decoration. The windows were wide, and beyond them there was a sort of
yard, with freshly planted trees. Over the whole setup there was a
fine crystal airdrome.

"What the heck! Where in the name of sense are we?" Harwich burst out
in startled pleasure.

He looked first at Paul Arnold, and then at Clara, whose amber eyes
were twinkling with secretive mischief. It was as though the two had
some sort of joke up their sleeves.

Harwich glanced again out of the window. Beyond the airdome, glinting
and new, was what looked like improved mining equipment. Cropping out
of the ground was the grayish, shiny stuff of a rich ore lode. And
there was a space ship, too; bright and slender and strange, but it
looked plenty serviceable!

"Where are we, anyway?" Harwich demanded again, still completely in the
dark. "Does either of you two know?"

"Still on Io, evidently!" Paul Arnold breezed with a taunting grin.
"Same kind of hills and general character of country! When Bayley shot
me, I passed out. I didn't know anything more until I woke up here a
little while ago!"

"But this layout, Paul!" Harwich growled. "This house and this mining
stuff! How come? You've got some kind of an answer in mind, I'm sure,
by the way you look! I give up. Spill the gag!"

"Okay, Evan," said the boy. "I really do think I've got that part
figured out! After Bayley shot you with the heat-pistol, you were
lying in that telepathy kiosk in the Tower room. Consciously or
unconsciously, you must have done some wishing there, before your brain
blacked out."

Harwich gasped. So that was it! He'd wanted to be alive, though he had
been mortally wounded. And so he was! His shirt was open. There was a
neat round scar on his chest, left by the heat-ray burn, and evidence
of careful supersurgery! The automatons of the Forbidden Moon had saved
his life. Probably Clara's and Paul's lives, too. All while they were
unconscious! The house, the garden, the mine!

"Our miracle hunt on the Forbidden Moon hasn't turned out so badly,"
Paul Arnold remarked. "But so far it's been a lot different from what
Dad or you or I could have anticipated. This place looks like a nice
family setup, Evan. Did you wish include anybody besides yourself?"

Harwich flushed, and looked sheepish. Clara, there, was definitely
blushing, but she was smiling, too.

The ex patrol pilot managed a nervous grin. "I guess you got me there,
Paul," he said. "Now, if it's all right with you, Clara, I don't know
whether I have to say it or not, since it's a dead giveaway. But will
you marry me?"

He got it out, feeling that it had been an awful job. But Clara smiled
happily.

"Try and stop me, Evan," she laughed. "There has to be someone around
to keep you from getting conceited. Just because you won out for us
here on Io, doesn't mean that you won't need bossing yourself, once in
a while!"

Paul Arnold winked, and left discreetly for other parts of the house.

Arm in arm Clara and Evan looked through a window that faced west.
Something was flying there, high up in the sky. It glinted in the late
afternoon sunlight. A lonely speck against the cold firmament, it
seemed to hurry, bent on a last mission.

A few minutes later, from the east, there came a terrific concussion.
The whole dark purple sky, above those sullen hills, was illuminated
with a bluish-white glare for a second. Flying fragments soared far
into space.

Clara clung tightly to Evan. "What was that?" she questioned fearfully.

Harwich grinned, but still there was a haunting shadow of sadness in
his face. "I'm sure I know," he said. "That was the end of the science
of the Forbidden Moon. The end of the force shield, apparatus, the
end of those poor Ionians, and the end of the pyramid! The end of the
whole thing. Suicide, you might call it. You see, back there in the
telepathy kiosk, I wished that too, and the machines were made only to
obey. I hope that when Earthmen, in the future, learn as much science
as existed here on Io, they'll know how to use it, too. We're much too
young a race yet, I guess."

Clara Arnold's awe softened after a moment. "Come on, Evan," she said.
"Let's forget all about that for now. I want to show you the kitchen,
here. It's ducky!..."