RIBBON IN THE SKY

                          BY MURRAY LEINSTER

                       Illustrated by van Dongen

           [Transcriber's Note: This etext was produced from
                 Astounding Science Fiction June 1957.
         Extensive research did not uncover any evidence that
         the U.S. copyright on this publication was renewed.]




                                   I


    "An error is a denial of reality, but mistakes are mere mental
    malfunctionings. In an emergency, a mistake may be made because of
    the need for precipitate action. There is no time to choose the best
    course: something must be done at once. Most mistakes, however,
    are made without any such exterior pressure. One accepts the
    first-imagined solution to a problem without examining it, either
    out of an urgent desire to avoid the labor of thinking, or out of
    impassioned reluctance to think about the matter at hand when
    prettier and more pleasurable other things can be contemplated...."

                                             _The Practice of Thinking_
                                                             Fitzgerald


It turned out afterward that somebody had punched the wrong button in
a computer. It was in a matter in which mistakes are not permissible,
but just as nothing can be manufactured without an ordinary hammer
figuring somewhere in the making or the making-ready-to-make, so
nothing can be done without a fallible human operating at some stage of
the proceedings. And humans make mistakes casually, off-handedly, with
impartial lack of malice, and unpredictability. So....

Calhoun heard the tape-speaker say, "_When the gong sounds, breakout
will follow in five seconds._" Then it made solemn ticking noises while
Calhoun yawned and put aside the book, "The Practice of Thinking," that
he'd been studying. Study was a necessity in his profession. Besides,
it helped to pass the time in overdrive. He went to the control-desk
chair and strapped in. Murgatroyd the _tormal_ uncoiled his tail from
about his nose and stood up from where he was catching twenty winks. He
padded to the place under Calhoun's chair where there were things to
grab hold of, if necessary, with four black paws and a prehensile tail.

"_Chee_," said Murgatroyd conversationally in his shrill treble.

"I agree," Calhoun told him gravely. "Stone walls do not a prison make,
nor Med Ship hulls a cage. But it will be good to get outside for a
change."

The tape-speaker ticked and tocked and ticked and tocked.
There was the sound of a gong. A voice said measuredly,
"_Five--four--three--two--one--_"

The ship came out of overdrive. Calhoun winced and swallowed. Nobody
ever gets used to going into overdrive or coming out of it. One is
hideously dizzy for an instant, and his stomach has a brief but violent
urge to upchuck, and no matter how often one has experienced it, it
is necessary to fight a flash of irrational panic caused by the two
sensations together.

But after an instant Calhoun stared about him as the vision-screens
came to life. They showed the cosmos outside the Med Ship. It was a
perfectly normal cosmos--not at all the cosmos of overdrive--but it
looked extremely wrong to Calhoun. He and Murgatroyd and the Med Ship
were in emptiness. There were stars on every hand, and they were of
every conceivable color and degree of brightness. But every one of them
was a point of light, and a point only.

This, obviously, was not what he'd expected. These days ships do not
stop to view the universe from the monstrous loneliness which is
Between-the-Stars. All ships go into overdrive as near their port
of departure as they can. Usually it is something like five or six
planetary diameters out from the local spaceport. All ships come out
of overdrive as near their destinations as computation makes possible.
They do not stop to look at scenery on the way. It isn't good for
humans to look at stars when there are only stars to see. The sight
has a tendency to make them feel small. Too small. Men have been known
to come out of such an experience gibbering.

Calhoun scowled at the sight of Between-the-Stars. This was not good.
But he wasn't frightened--not yet. There should have been a flaming
sun somewhere nearby, and there should have been bright crescents
or half-disks or mottled cloudy planets swimming within view. The
sun should have been the star Merida, and Calhoun should land in
commonplace fashion on Merida II and make a routine planetary health
check on a settled, complacent population, and presently he should head
back to Med Headquarters with a report containing absolutely nothing of
importance. But he couldn't do any of these things. He was in purely
empty space. It was appalling.

       *       *       *       *       *

Murgatroyd jumped up to the arm of the control-chair, to gaze wisely at
the screens. Calhoun continued to scowl. Murgatroyd imitated him with a
_tormal's_ fine complacency in duplicating a man's actions. What he saw
meant nothing to him, of course. But he was moved to comment.

"_Chee_," he said shrilly.

"To be sure," agreed Calhoun distastefully. "That is a very sage
observation, Murgatroyd. But I deplore the situation that calls for it.
Somebody's bilged on us."

Murgatroyd liked to think that he was carrying on a conversation. He
said zestfully:

"_Chee-chee! Chee-chee-chee!_"

"No doubt," conceded Calhoun. "But this is a mess! Hop down and let me
try to get out of it."

Murgatroyd disappointedly hopped to the floor. He watched with bright
eyes as Calhoun annoyedly went to the emergency-equipment locker and
brought out the apparatus designed to take care of a state of things
like this. If the situation wasn't too bad, correcting it should be
simple enough. If it was too bad, it could be fatal.

The average separation of stars throughout the galaxy, of course, is
something like four or five light-years. The distance between sol-type
stars is on an average very much higher, and with certain specific
exceptions habitable planets are satellites of sol-type suns. But only
a fraction of the habitable planets are colonized, and when a ship has
traveled blind, in overdrive, for two months or more its pilot cannot
simply look astern and recognize his point of departure. There's too
much scenery in between. Further, nobody can locate himself by the use
of star-maps unless he knows where something on the star-map is, with
reference to himself. Which makes a star-map not always useful.

But the present blunder might not be serious. If the Med Ship had
come out into normal space no more than eight to ten light-years from
Merida, Calhoun might identify that sun by producing parallax. He
could detect relative distances for a much greater range. But it was to
be hoped that his present blunder was small.

He got out the camera with its six lenses for the six vision-screens
which showed space in all directions. He clamped it in place and
painstakingly snapped a plate. In seconds he had everything above third
magnitude faithfully recorded in its own color, and with relative
brightnesses expressed in the size of the dots of tint. He put the
plate aside and said:

"Overdrive coming, Murgatroyd."

He pressed the short-hop button and there was dizziness and nausea
and a flash of fear--all three sensations momentary. Murgatroyd said,
"_Chee_" in a protesting tone, but Calhoun held down the button for an
accurate five minutes. He and Murgatroyd gulped together when he let
up the button again and all space whirled and nausea hit as before. He
took another plate of all the heavens, made into one by the six-lensed
camera. He swung the ship by ninety degrees and pressed the short-hop
button a second time. More dizziness and panic and digestive revolt. In
five minutes it was repeated as the ship came out to normal space yet
again.

"_Chee-chee!_" protested Murgatroyd. His furry paws held his round
little belly against further insult.

"I agree," said Calhoun. "I don't like it either. But I want to know
where we are--if anywhere."

He set up the comparator and inserted the three plates. Each had
images of each of the six vision-screens. When the instrument whirred,
each of the plates in turn was visible for part of a second. Extremely
remote stars would not jiggle perceptibly--would not show parallax--but
anything within twenty light-years should. The jiggling distance could
be increased by taking the plates still farther apart. This time,
though, there was one star which visibly wavered in the comparator.
Calhoun regarded it suspiciously.

"We're Heaven knows where," he said dourly. "Somebody really messed us
up! The only star that shows parallax isn't Merida. In fact, I don't
believe in it at all! Two plates show it as a sol-class sun and the
third says it's a red dwarf!"

On the face of it, such a thing was impossible. A sun cannot be one
color as seen from one spot, and another color seen from another.
Especially when the shift of angle is small.

Calhoun made rough computations. He hand-set the overdrive for
something over an hour's run in the direction of the one star-image
which wabbled and thereby beckoned. He threw the switch. He gulped, and
Murgatroyd acted for a moment as if he intended to yield unreservedly
to the nausea of entering overdrive. But he refrained.

       *       *       *       *       *

There was nothing to do but kill time for an hour. There was a
micro-reel of starplates, showing the heavens as photographed with the
same galactic co-ordinates from every visited sol-class star in this
sector of the galaxy. Fewer than one in forty had a colonized planet,
but if the nearest had been visited before, and if the heavens had been
photographed there, by matching the stars to the appropriate plate he
could find out where he was. Then a star-map might begin to be of some
use to him. But he had still to determine whether the error was in his
astrogation unit, or in the data fed to it. If the first, he'd be very
bad off indeed. If the second, he could still be in a fix. But there
was no point in worrying while in overdrive. He lay down on his bunk
and tried to concentrate again on the book he'd laid aside.

"_Human error, moreover_," he read, "_is never purely random. The mind
tends to regard stored data as infallible and to disregard new data
which contradicts it...._" He yawned, and skipped. "... _So each person
has a personal factor of error which is not only quantitative but
qualitative...._"

He read on and on, only half absorbing what he read. But a man who
has reached the status of a Med Ship man in the Interstellar Medical
Service hasn't finished learning. He's still away down the ladder of
rank. He has plenty of studying ahead of him before he gets very far.

The tape-speaker said, "_When the gong sounds, breakout will be five
seconds off._" It began to _ticktock_, slowly and deliberately.
Calhoun got into the control seat and strapped in. Murgatroyd said
peevishly, "_Chee!_" and went to position underneath the chair. The
voice said, "_Five--four--three--two--one--_"

The little Med Ship came out of overdrive, and instantly its emergency
rockets kicked violently and Murgatroyd held desperately fast. Then the
rockets went off. There'd been something unguessable nearby--perhaps
cometary debris at the extremest outer limit of a highly eccentric
orbit. Now there was a starfield and a sun within two light-hours. But
if Calhoun had stared, earlier, when there was no sun in sight at all,
now he gazed blankly at the spectacle before him.

There was a sun off to starboard. It was a yellow sun--a sol-type
star with a barely perceptible disk. There were planets. Calhoun saw
immediately one gas-giant near enough to be more than a point, and a
sliver of light which was the crescent of another more nearly in line
toward the sun. But he gazed at a belt, a band, a ribbon of shining
stuff which was starkly out of all reason.

It was a thin curtain of luminosity circling this yellow star. It was
not a ring from the breakup of a satellite within Roche's Limit. There
were two quite solid planets inside it and nearer to the star. It
was a thin, wide, luminous golden ribbon which looked like something
that needed a flatiron to smooth it out. It looked something like an
incandescent smoke ring. It was not smooth. It had lumps in it. There
were corrugations in it. An unimaginable rocket with a flat exhaust
could have made it while chasing its tail around the sun. But that
couldn't have happened, either.

Calhoun stared for seconds.

"Now," he said, "I've seen everything!" Then he grunted as realization
came. "And we're all right, Murgatroyd! It's not our computers that
went wrong. Somebody fed them wrong data. We arrived where we aimed
for, and there'll be a colonized planet somewhere around."

He unlimbered the electron telescope and began a search. But he
couldn't resist a closer look at the ribbon in space. It had exactly
the structure of a slightly wabbly wrinkled ribbon without beginning
or end. It had to be a complex of solid particles, of course, and
an organization of solid particles cannot exist in space without
orbital motion. But orbits would smooth out in the course of thousands
of revolutions around a primary. This was not smoothed out. It was
relatively new.

"It's sodium dust," said Calhoun appreciatively. "Or maybe potassium.
Hung out there on purpose. Particles small enough to have terrific
surface and reflective power, and big enough not to be pushed out of
orbit by light-pressure. Clever, Murgatroyd! At a guess it'll have been
put out to take care of the climate on a planet just inside it. Which
would be--there! Let's go look!"

He was so absorbed in his admiration that the almost momentary
overdrive-hop needed for approach went nearly unnoticed. He even
realized--his appreciation increasing--that this cloud of tiny
particles accounted for the red-dwarf appearance on one of the plates
he'd taken. Light passing through widely dispersed and very small
particles turns red. From one position, he'd photographed through this
dust cloud.

The ribbon was a magnificent idea--the more magnificent because of
its simplicity. It would reflect back otherwise wasted sun-heat to
a too-cold planet and make it warmer. There was probably only an
infinitesimal actual mass of powder in the ring, at that. Tens or
scores of tons in all. Hardly more.

The planet for which it had been established was the third world out.
As is usual with sol-class systems, the third planet's distance from
the sun was about a hundred twenty million miles. It had icecaps
covering more than two-thirds of its surface. The sprawling white
fingers of glaciation marked mountain chains and highlands nearly
to the equator. But there was some blue sea, and there was green
vegetation in a narrow belt of tropicality.

Calhoun jockeyed the Med Ship to position for a landing call. This was
not Merida II, but there should be a colony here. That glowing ribbon
had not been hung out for nothing.

"Med Ship Esclipus Twenty," he said confidently into the spacephone
mike. "Calling ground. Requesting co-ordinates for landing. My mass is
fifty tons. Repeat, five-oh tons. Purpose of landing, to find out where
I am and how to get where I belong."

There was a clicking. Calhoun repeated the call. He heard murmurings
which were not directed into the transmitter on the planet. He heard an
agitated, "_How long since a ship landed?_" Another voice was saying
fiercely, "_Even if he doesn't come from Two City or Three City, who
knows what sickness_--" There was sudden silence, as if a hand had been
clapped over the microphone below. Then a long pause. Calhoun made the
standard call for the third time.

"_Med Ship Esclipus Twenty_," said the spacephone speaker grudgingly,
"_You will be allowed to land. Take position_--" Calhoun blinked at
the instructions he received. The co-ordinates were not the normal
galactic ones. They gave the local time at the spaceport, and the
planetary latitude. He was to place himself overhead. He could do it,
of course, but the instructions were unthinkable. Galactic co-ordinates
had been used ever since Calhoun knew anything about such matters. But
he acknowledged the instructions. Then the voice from the speaker said
truculently: "_Don't hurry! We might change our minds! And we have to
figure settings for an only fifty-ton ship, anyhow._"

Calhoun's mouth dropped open. A Med Ship was welcome everywhere, these
days. The Interstellar Medical Service was one of those overworked,
understaffed, kicked-around organizations which is everywhere taken for
granted. Like breathable air, nobody thought to be grateful for it--but
nobody was suspicious of it, either.

The suspicion and the weird co-ordinates and the ribbon in space
combined to give Calhoun a highly improbable suspicion. He looked
forward with great interest to this landing. He had not been ordered to
land here, but he suspected that a Med Ship landing was a long, long
time overdue.

"I forgot to take star-pictures," he told Murgatroyd, "but a ribbon
like this would have been talked about if it had been reported before.
I doubt star-pictures would do us any good. The odds are our only
chance to find out where we are is to ask." Then he shrugged his
shoulders. "Anyhow this won't be routine!"

"_Chee!_" agreed Murgatroyd, profoundly.




                                  II


    "An unsolvable but urgent problem may produce in a society, as in an
    individual, an uncontrollable emotional tantrum, an emotional denial
    of the problem's existence, or purposive research for a solution. In
    olden days, the first reaction produced mass-tantrums then called
    'wars.' The second produced frenziedly dogmatic ideologies. The
    third produced modern civilization. All three reactions still appear
    in individuals. If the first two should return to societies, as
    such...."

                                             _The Practice of Thinking_
                                                             Fitzgerald


The descent, at least, was not routine. It was nerve-racking. The
force-field from the planet's giant steel landing grid reached out into
space and fumbled for the Med Ship. That was clumsily done. When it
found the ship, it locked on. And that was awkwardly handled. The rest
was worse. Whoever handled the controls, aground, was hopelessly inept.
Once the Med Ship's hull-temperature began to climb, and Calhoun had to
throw on the spacephone and yelp for caution. He did not see as much of
the nearing planet as he'd have liked.

At fifty miles of height, the last trace of blue sea vanished around
the bulge of the world. At twenty miles, the mountain chains were
clearly visible, with their tortured, winding ice rivers which were
glaciers. At this height three patches of green were visible from
aloft. One, directly below, was little more than a mile in diameter and
the landing grid was its center and almost its circumference. Another
was streaky and long, and there seemed to be heavy mist boiling about
it and above it. The third was roughly triangular. They were many miles
apart. Two of them vanished behind mountains as the ship descended.

There were no cities in view. There were no highways. This was an
ice world with bare ground and open water at its equator only. The
spaceport was placed in a snow-ringed polar valley.

Near landing, Calhoun strapped in because of the awkwardness with which
the ship was lowered. He took Murgatroyd on his lap. The small craft
bounced and wabbled as unskilled hands let it down. Presently, Calhoun
saw the angular girders of the landing grid's latticed top rise past
the opened ports. Seconds later, the Med Ship bumped and slid and
bounced heart-stoppingly. Then it struck ground with a violent jolt.

Calhoun got his breath back as the little ship creaked and adjusted
itself to rest on its landing fins after some months in space.

"_Now_," said the voice in the spacephone speaker--but it sounded as if
it were trying to conceal relief--"_now stay in your ship. Our weapons
are bearing on you. You may not come out until we've decided what to do
about you._"

Calhoun raised his eyebrows. This was very unusual indeed. He glanced
at the external field indicator. The landing grid field was off. So the
operator bluffed. In case of need Calhoun could blast off on emergency
rockets and probably escape close-range weapons anyhow--if there were
any--and he could certainly get around the bulge of the world before
the amateur at the grid's controls could hook on to him again.

"Take your time," he said with irony. "I'll twiddle my fingers. I've
nothing better to do!"

He freed himself from his chair and went to a port to see. He regarded
the landscape about him with something like unbelief.

       *       *       *       *       *

The landing grid itself was a full mile across and half as high. It was
a vast, circular frame of steel beams reaching heavenward, with the
curiously curving copper cables strung as they had to be to create the
highly special force-field which made space transportation practical.
Normally such gigantic structures rose in the centers of spaceport
cities. They drew upon the planet's ionosphere for power to lift
and land cargo ships from the stars, and between-times they supplied
energy for manufactures and the operation of cities. They were built,
necessarily, upon stable bedrock formations, and for convenience were
usually located where the cargoes to be shipped would require least
surface transportation.

But here there was no city. There was perhaps a thousand acres of
greenness--a mere vague rim around the outside of the grid. There was
a control-room building to one side, of course. It was solidly built
of stone, but there had been an agglomeration of lean-tos added to it
with slanting walls and roofs of thin stratified rock. And there were
cattle grazing on the green grass. The center of the grid was a pasture!

Save for the clutter about the grid-control building there were no
structures, no dwellings, no houses or homes anywhere in view. There
was no longer even a highway leading to the grid. Calhoun threw on the
outside microphones and there was no sound except a thin keening of
wind in the steelwork overhead. But presently one of the cattle made a
mournful bellowing sound.

Calhoun whistled as he went from one port to another.

"Murgatroyd," he said meditatively on his second round, "you
observe--if you observe--one of the consequences of human error. I
still don't know where I am, because I doubt that starplates have ever
been made from this solar system, and I didn't take one for comparison
anyhow. But I can tell you that this planet formerly had a habitability
rating of something like oh point oh, meaning that if somebody wanted
to live here it would be possible but it wouldn't be sensible. But
people did come here, and it was a mistake."

He stared at a human figure, far away. It was a woman, dressed in
shapeless, badly draping garments. She moved toward a clump of
dark-coated cattle and did something in their midst.

"The mistake looks pretty evident to me," added Calhoun, "and I see
some possibilities I don't like at all. There is such a thing as an
isolation syndrome, Murgatroyd. A syndrome is a complex of pathological
symptoms which occur together as a result of some morbid condition. To
us humans, isolation is morbid. You help me to endure it, Murgatroyd,
but I couldn't get along with only your society--charming as it is--for
but so long. A group of people can get along longer than a single man,
but there is a limit for any small-sized group."

"_Chee_," said Murgatroyd.

"In fact," said Calhoun, frowning, "there's a specific health problem
involved, which the Med Service recognizes. There can be partial
immunity, but there can be some tricky variations. If we're up against
a really typical case we have a job on hand. And how did these people
get that dust-ring out in space? They surely didn't hang it out
themselves!"

He sat down and scowled at his thoughts. Presently he rose again and
once more surveyed the icy landscape. The curious green pasture about
the landing grid was highly improbable. He saw glaciers over-hanging
this valley. They were giant ice rivers which should continue to flow
and overwhelm this relatively sheltered spot. They didn't. Why not?

       *       *       *       *       *

It was more than an hour before the spacephone clattered. When Calhoun
threw the switch again a new voice came out of it. This was also a
male voice, but it was high-pitched as if from tension.

"_We've been talking about you_," said the voice. It quivered with
agitation which was quite out of reason. "_You say you're Med Service.
All right. Suppose you prove it!_"

The landed Med Ship should be proof enough for anybody. But Calhoun
said politely:

"I have the regular identifications. If you'll go on vision, I'll show
you my credentials."

"_Our screen's broken_," said the voice, suspiciously, "_but we have
a sick cow. It was dumped on us night before last. Cure her and we'll
accept it as identification._"

Calhoun could hardly believe his ears. This was an emergency situation!
The curing of a sick cow was considered more convincing than a Med Ship
man's regular credentials! Such a scale of values hinted at more than
a mere isolation syndrome. There were thousands of inhabited worlds,
now, with splendid cities and technologies which most men accepted with
the same bland confidence with which they looked for sunrise. The human
race was civilized. Suspicion of a Med Ship was unheard of. But here
was a world--

"Why ... certainly," said Calhoun blankly. "I suppose I may go outside
to ... ah ... visit the patient?"

"_We'll drive her up to your ship_," said the high, tense voice. "_And
you stay close to it!_" Then it said darkly. "_Men from Two City
sneaked past our sentries to dump it on us. They want to wipe out our
herd! What kind of weapons have you got?_"

"This is a Med Ship!" protested Calhoun. "I've nothing more than I
might need in an emergency!"

"_We'll want them anyhow_," said the voice. "_You said you need to find
out where you are. We'll tell you, if you've got enough weapons to make
it worth while._"

Calhoun drew a deep breath.

"We can argue that later," he said. "I'm just a trifle puzzled. But
first things first. Drive your cow."

He held his head in his hands. He remembered to throw off the
spacephone and said:

"Murgatroyd, say something sensible! I never ran into anybody quite as
close to coming apart at the seams as that! Not lately! Say something
rational!"

Murgatroyd said, "_Chee?_" in an inquiring tone.

"Thanks," said Calhoun. "Thanks a lot."

He went back to the ports to watch. He saw men come out of the peculiar
agglomeration of buildings that had been piled around the grid's sturdy
control building. They were clothed in cloth that was heavy and very
stiff, to judge by the way it shifted with its wearers' movements.
Calhoun wasn't familiar with it. The men moved stolidly, on foot,
across the incredible pasture which had been a landing space for ships
of space at some time or other.

They reached a spot where a dark animal form rested on the ground.
Calhoun hadn't noticed it particularly. Cattle, he knew, folded their
legs and lay down and chewed cuds. They existed nearly everywhere
that human colonies had been built. On some worlds there were other
domestic animals descended from those of Earth. Of course there were
edible plants and some wholesome animals which had no connection at all
with humanity's remote ancestral home, but from the beginning human
beings had been adjusted to symbiosis with the organic life of Earth.
Foodstuffs of non-terrestrial origin could supplement Earth-food, of
course. In some cases Earth-foods were the supplements and local,
non-terrestrial foodstuffs the staples. But human beings did not thrive
on a wholly un-Earthly diet.

The clump of slowly moving men reached the reclining cow. They pulled
up stakes which surrounded her, and coiled up wire or cordage which had
made the stakes into a fence. They prodded the animal. Presently it
lurched to its feet and swung its head about foolishly. They drove it
toward the Med Ship.

Fifty yards away they stopped, and the outside microphones brought the
sound of their voices muttering. By then Calhoun had seen their faces.
Four of the six were bearded. The other two were young men. On most
worlds men prided themselves that they needed to shave, but few of them
omitted the practice.

These six moved hastily away, though the two younger ones turned often
to look back. The cow, deserted, stumbled to a reclining position. It
lay down, staring stupidly about. It rested its head on the ground.

"I go out now, eh?" asked Calhoun mildly.

"_We're watching you!_" grated the spacephone speaker.

Calhoun glanced at the outside temperature indicator and added a
garment. He put a blaster in his pocket. He went out the exit port.

       *       *       *       *       *

The air was bitter cold, after two months in a heat-metered ship, but
Calhoun did not feel cold. It took him seconds to understand why.
It was that the ground was warm. Radiant heat kept him comfortable,
though the air was icy. Heat elements underground must draw power
from somewhere--the grid's tapping of the ionosphere--and heated this
pasture from underneath so forage plants could grow here. They did.
The cattle fed on them. There would be hydroponic gardens somewhere
else, probably underground. They would supply vegetable food in greater
quantity. But in the nature of things human beings had to have animal
food in a cold climate.

Calhoun went across the pasture with the frowning snowy mountains
all about. He regarded the reclining beast with an almost humorous
attention. He did not know anything about the special diseases of
domestic animals. He had only the knowledge required of a Med Ship man.
But that should be adequate. The tense voice had said that this beast
had been "dumped," to "wipe out" the local herd. So there would be
infection and there would be some infective agent.

He painstakingly took samples of blood and saliva. In a ruminant,
certainly, any digestive-tract infection should show up in the saliva.
He reflected that he did not know the normal bovine temperature, so he
couldn't check it. Nor the respiration. But the Interstellar Medical
Service was not often called on to treat ailing cows.

Back in the ship he diluted his samples and put droplets in the usual
nutrient solutions. He sealed up droplets in those tiny slides which
allow a culture to be examined as it grows. His microscope, of course,
allowed of inspection under light of any wave length desired, and so
yielded information by the frequency of the light which gave clearest
images of different features of microörganisms.

After five minutes of inspection he grunted and hauled out his
antibiotic stores. He added infinitesimal traces of cillin to the
culture-media. In the microscope, he watched the active microscopic
creatures die. He checked with the other samples.

He went out to the listless, enfeebled animal. He made a wry guess at
its body-weight. He used the injector. He went back to the Med Ship. He
called on the spacephone.

"I think," he said politely, "that your beast will be all right in
thirty hours or so. Now, how about telling me the name of this sun?"

The voice said sharply:

"_There's a matter of weapons, too! Wait till we see how the cow does!
Sunset will come in an hour. When day comes again, if the cow is
better--we'll see!_"

There was a click. The spacephone cut off.

       *       *       *       *       *

Calhoun pulled out the log-mike. There was already an audio record
of all ship-operations and communications. Now he added comments--a
description of the ribbon in the sky, the appearance of the planet, and
such conclusions as he'd come to. He ended:

"... The samples from the cow were full of a single coccus, which
seemed to have no resistance to standard antibiotics. I pumped the
beast full of cillin and called it a day. I'm concerned, though,
because of the clear signs of an isolation syndrome here. They're
idiotically suspicious of me and won't even promise a bargain, as if I
could somehow overreach them because I'm a stranger. They've sentries
out--they said somebody sneaked past them--against what I imagine must
be Two City and Three City. I've an impression that the sentries are
to enforce a quarantine rather than to put up a fight. It is probable
that the other communities practice the same tactics--plus biological
cold war if somebody did bring a sick cow here to infect and destroy
the local herd. These people may have a landing grid, but they've
an isolation syndrome and I'm afraid there's a classic Crusoe health
problem in being. If that's so, it's going to be nasty!"

He cut off the log. The classic Crusoe problem would be extremely
awkward if he'd run into it. There was a legend about an individual
back on old Earth who'd been left isolated on an island by shipwreck
for half a lifetime. His name was given to the public-health
difficulties which occurred when accidental isolations occurred during
the chaotic first centuries of galactic migration. There was one
shipwreck to which the name was first applied. The ship was missing,
and the descendants of the crew and passengers were not contacted until
three generations had passed. Larger-scale and worse cases occurred
later, when colonies were established by entrepreneurs who grew rich
in the establishment of the new settlements, and had no interest in
maintaining them. Such events could hardly happen now, of course, but
even a Crusoe condition was still possible in theory. It might exist
here. Calhoun hoped not.

It did not occur to him that the affair was not his business because
he hadn't been assigned to it. He belonged to the Med Service, and
the physical well-being of humans everywhere was the concern of that
service. If people lived by choice in an inhospitable environment, that
was not a Med man's problem, but anything which led to preventable
deaths was. And in a Crusoe colony there were plenty of preventable
deaths!

He cooked a meal to have something to occupy his mind. Murgatroyd sat
on his haunches and sniffed blissfully. Presently Calhoun ate, and
again presently darkness fell on this part of the world. There were new
noises--small ones. He went to look. The pasture inside the landing
grid was faintly lighted by the glowing ribbon in the sky. It looked
like a many-times-brighter Milky Way. The girders of the landing grid
looked very black against it.

He saw a dark figure plodding away until he vanished. Then he
reappeared as a deeper black against the snow beyond the pasture. He
went on and on until he disappeared again. A long time later another
figure appeared where he'd gone out of sight. It plodded back toward
the grid. It was a different individual. Calhoun had watched a changing
of sentries. Suspicion. Hostility. The least attractive qualities of
the human race, brought out by isolation.

There could not be a large population here, since such suspicions
existed. And it was divided into--most likely--three again-isolated
communities. This one had the landing grid, which meant power, and
a spacephone but no vision screen attached to it. The fact that
there were hostile separate communities made the situation much more
difficult, from a medical point of view. It multiplied the possible
ghastly features which could exist.

Murgatroyd ate until his furry belly was round as a ball, and settled
to stuffed slumber with his tail curled around his nose. Calhoun tried
to read. But he was restless. His own time-cycle on the ship did not
in the least agree with the time of daylight on this planet. He was
wakeful when there was utter quiet outside. Once one of the cattle made
a dismal lowing noise. Twice or three times he heard cracking sounds,
like sharp detonations, from the mountains. They would be stirrings in
the glaciers.

He tried to study, but painstaking analysis of the methods by which
human brains defeated their own ends and came up with wrong answers was
not appealing. He grew horribly restless.

       *       *       *       *       *

It had been dark for hours when he heard rustling noises on the
ground outside--through the microphones, of course. He turned up the
amplification and made sure that a small party of men moved toward the
Med Ship. From time to time they paused, as if in caution.

"Murgatroyd," he said dryly, "we're going to have visitors. They didn't
give notice by spacephone, so they're unauthorized."

Murgatroyd blinked awake. He watched as Calhoun made sure of the
blaster in his pocket and turned on the log-mike. He said:

"All set, Murgatroyd?"

Murgatroyd said "_Chee_" in his small shrill voice just as a soft and
urgent knock sounded on the exit-lock door. It was made with bare
knuckles. Calhoun grimaced and went into the lock. He undogged the door
and began to open it, when it was whipped from his grasp and plunging
figures pushed in. They swept him back into the Med Ship's cabin. He
heard the lock-door close softly. Then he faced five roughly, heavily
clothed men who wore cloaks and mittens and hoods, with cloth stretched
tightly across their faces below the eyes. He saw knives, but no
blasters.

A stocky figure with cold gray eyes appeared as spokesman.

"You're the man who got landed today," he said in a deep voice and with
an effect of curtness. "My name's Hunt. Two City. You're a Med Ship
man?"

"That's right," said Calhoun. The eyes upon him were more scared than
threatening--all but the stocky man named Hunt. "I landed to find out
where I was," he added. "The data-card for my astrogator had been
punched wrong. What--"

"You know about sickness, eh?" demanded the stocky man evenly. "How to
cure it and stop it?"

"I'm a Med Ship man," admitted Calhoun. "For whatever that may mean."

"You're needed in Two City," said the deep-voiced Hunt. His manner was
purest resolution. "We came to get you. Get y'medicines. Dress warm.
Load us down, if you like, with what you want to take. We got a sledge
waiting."

Calhoun felt a momentary relief. This might make his job vastly
easier. When isolation and fear brings a freezing of the mind against
any novelty--even hope--a medical man has his troubles. But if one
community welcomed him--

"_Chee!_" said Murgatroyd indignantly from overhead. Calhoun glanced
up and Murgatroyd glared from a paw-hold near the ceiling. He was a
peaceable animal. When there was scuffling he got out of the way. But
now he chattered angrily. The masked men looked at him fearfully. But
their deep-voiced leader growled at them.

"Just a animal." He swung back to Calhoun. "We got a need for you," he
repeated. "We mean all right, and anything we got you can have if you
want it. But you're coming with us!"

"Are your good intentions," asked Calhoun, "proved by your wearing
masks?"

"They're to keep from catchin' your sickness," said the deep voice
impatiently. "Point to what you want us to take!"

Calhoun's feeling of encouragement vanished. He winced a little. The
isolation syndrome was fully developed. It was a matter of faith that
strangers were dangerous. All men were assumed to carry contagion.
Once, they'd have been believed to carry bad luck. But a regained
primitiveness would still retain some trace of the culture from which
it had fallen. If there were three settlements as the pastureslands
seen from space suggested, they would not believe in magic, but they
would believe in contagion. They might have, or once have had, good
reason. Anyhow they would fanatically refrain from contact with any but
their own fellow-citizens. Yet there would always be troubles to excite
their terrors. In groups of more than a very few there would always be
an impulse against the isolation which seemed the only possible safety
in a hostile world. The effectiveness of the counter-instinct would
depend in part on communications, but the urge to exogamy can produce
ghastly results in a small culture gone fanatic.

"I think," said Calhoun, "that I'd better come with you. But the people
here have to know I've gone. I wouldn't like them to heave my ship out
to space in pure panic because I didn't answer from inside it!"

"Leave a writing," said Hunt's deep voice, as impatiently as before.
"I'll write it. Make them boil, but they don't dare follow us!"

"No?"

"Think One City men," asked the stocky man scornfully, "will risk us
toppling avalanches on them?"

Calhoun saw. Amid mountain-country in a polar zone, travel would be
difficult at best. These intruders had risked much to come here for
him. But they were proud of their daring. They did not believe that
the folk of lesser cities--tribes--groups than theirs had courage like
theirs. Calhoun recognized it as a part of that complex of symptoms
which can begin with an epidemic and end with group-madness.

"I'll want this--and this--and that," said Calhoun. He wouldn't risk
his microscope. Antibiotics might be useful. Antiseptics, definitely.
His med-kit--"That's all."

"Your blankets," said Hunt. "Y'want them, too."

Calhoun shrugged. He clothed himself for the cold outside. He had
a blaster in his pocket, but he casually and openly took down a
blast-rifle. His captors offered no objection. He shrugged again and
replaced it. Starting to take it was only a test. He made a guess that
this stocky leader, Hunt, might have kept his community just a little
more nearly sane than the group that had set him to the cure of a sick
cow. He hoped so.

"Murgatroyd," he said to the _tormal_ still clinging up near the
control-room's top, "we have a professional call to make. You'd better
come along. In fact, you must."

Murgatroyd came suspiciously down, and then leaped to Calhoun's
shoulder. He clung there, gazing distrustfully about. Calhoun realized
that his captors--callers--whatever they were--stayed huddled away from
every object in the cabin. They fingered nothing. But the scared eyes
of most of them proved that it was not honesty which moved them to such
meticulousness. It was fear. Of contagion.

"They're uncouth, eh?" said Calhoun sardonically. "But think,
Murgatroyd, they may have hearts of gold! We physicians have to
pretend to think so, in any case!"

"_Chee!_" said Murgatroyd resentfully as Calhoun moved toward the lock.




                                  III


    "Civilization is based upon rational thought applied to the purposes
    of men. Most mistakes occur in the process of thinking. But there
    can be a deep and fundamental error about purposes. It is simply a
    fact that the purposes of human beings are not merely those of
    rational animals. It is the profoundest of errors to believe
    otherwise--to consider, for example, that prosperity, or pleasure,
    or even survival, cannot be priced so high that their purchase is a
    mistake."

                                             _The Practice of Thinking_
                                                             Fitzgerald


There was a sheet of paper fastened outside the combination lock of
the Med Ship's exit port. It said that Calhoun had been taken away by
men of Two City, to tend some sick person. It said that he would be
returned. The latter part might not be believed, but the Med Ship might
not be destroyed. The colony of the landing grid might try to break
into it, but success was unlikely.

Meanwhile, it was an odd feeling to cross the grassy pastureland with
hoarfrost crunching underfoot. The grid's steel girders made a harsh
lace of blackness against the sky, with its shining ribbon slashing
across it. But Calhoun found himself reflecting that the underground
heat applied to the thousand-acre pasture had been regulated with
discretion. There was surely power enough available from the grid to
turn the area into a place of tropic warmth, in which only lush and
thick-leaved vegetation could thrive. But a storm from the frigid
mountains would destroy such plants. Hardy, low-growing, semi-arctic
grass was the only suitable ground-cover. The iciest of winds could not
freeze it so long as the ground was warmed.

Tonight's wind was biting. Calhoun had donned a parka of synthetic fur
on which frost would not congeal at any temperature, but he was forced
to draw fur before his face and adjust heated goggles before his eyes
would stop watering. Yet in the three-quarter-mile trudge to the edge
of the snow, his feet became almost uncomfortably warm.

That, though, ended where a sledge waited at the edge of the snow. Five
men had forced themselves inside the Med Ship. A sixth was on guard
beside the sledge. There had been no alarm. Now the stocky man, Hunt,
urged him to a seat upon the sledge.

"I'm reasonably able-bodied," said Calhoun mildly.

"You don't know where we're going--or how," growled Hunt.

Calhoun got on the sledge. The runners were extraordinarily long. He
could not see small details, but it appeared that the sledge had been
made of extreme length to bridge crevasses in a glacier. There were
long thin metal tubes to help. At the same time, it looked as if it
could be made flexible to twist and turn in a narrow or obstacle-strewn
path.

The six clumsily-clad men pushed it a long way, while Calhoun frowned
at riding. Then Murgatroyd shivered, and Calhoun thrust him inside the
parka. There Murgatroyd wriggled until his nose went up past Calhoun's
chin and he could sniff the outside air. From time to time he withdrew
his nose--perhaps with frost-crystals on it. But always he poked his
small black snout to sniff again. His whiskers tickled.

Two miles from the pastureland, the sledge stopped. One man fumbled
somewhere behind Calhoun's seat and a roaring noise began. All six
piled upon the long, slender snow-vehicle. It began to move. A man
swore. Then, suddenly, the sledge darted forward and went gliding up
a steep incline. It gathered speed. Twin arcs of disturbed snow rose
up on either side, like bow-waves from a speeding water-skimmer. The
sledge darted into a great ravine of purest white and the roaring sound
was multiplied by echoes.

For better than half an hour, then, Calhoun experienced a ride which
for thrills and beauty and hair-raising suspense made mere space-travel
the stodgiest of transportation. Once the sledge shot out from beetling
cliffs--all icy and glittering in the light from the sky--and hurtled
down a slope of snow so swiftly that the wind literally whistled about
the bodies of its occupants. Then the drive roared more loudly, and
there was heavy deceleration, and abruptly the sledge barely crawled.
The flexibility of the thing came into operation. Four of the crew,
each controlling one segment of the vehicle, caused it to twist and
writhe over the surface of a glacier, where pressure-ridges abounded
and pinnacles of shattered, squeezed-up ice were not uncommon.

Once they stopped short and slender rods reached out and touched, and
the sledge slid delicately over them and was itself a bridge across a
crevasse in the ice that went down unguessably. Then it went on and
the rods were retrieved. Minutes later the sledge-motor was roaring
loudly, but it barely crawled up to what appeared to be a mountain
crest--there were ranges of mountains extending beyond seeing in the
weird blue-and-golden skylight--and then there was a breathtaking dash
and a plunge into what was incredibly a natural tunnel beside the
course of an ice-river--and abruptly there was a vast valley below.

This was their destination. Some thousands of feet down in the very
valley-bottom there was a strange, two-mile-long patch of darkness.
The blue-gold light showed no color there, but it was actually an
artificially warmed pastureland like that within and about the landing
grid. But from this dark patch vapors ascended, and rolled, and
gathered to form a misty roof--which was swept away and torn to tatters
by an unseen wind.

The sledge slowed and stopped beside a precipitous upcrop of stone
while still high above the valley bottom. A voice called sharply:

"It's us," growled Hunt's deep voice. "We got him. Everything all
right?"

... "No!" rasped the invisible voice. "They broke out--he broke out and
got her loose, and they run off again. We shoulda killed 'em and had
done with it!"

Everything stopped. The men on the sledge seemed to become still in
the shock of pure disaster, pure frustration. Calhoun waited. Hunt was
motionless. Then one of the men on the sledge spat elaborately. Then
another stirred.

"Had your work for nothing," rasped the voice from the shadow. "The
trouble that's started goes for nothing, too!"

Calhoun asked crisply:

"What's this? My special patients ran away?"

"That the Med man we heard about?" The invisible speaker was almost
derisive with anger. "Sure! They've run off, all right! Man and girl
together. After we made trouble with Three City by not killin' 'em and
One City by sneakin' over to get you! Three City men'll come boiling
over--" The voice raised in pitch, expressing scorn and fury. "Because
they fell in love! We shoulda killed 'em right off or let 'em die in
the snow like they wanted in the first place!"

       *       *       *       *       *

Calhoun nodded almost imperceptibly to himself. When there is a
syndrome forbidding association between societies, it is a part
of the society's interior struggle against morbidity that there
shall be forbidden romances. The practice of exogamy is necessary
for racial health, hence there is an instinct for it. The more
sternly a small population restricts its human contacts to its own
members, the more repressed the exogamic impulse becomes. It is never
consciously recognized for what it is. But especially when repressed,
other-than-customary contacts trigger it explosively. The romantic
appeal of a stranger is at once a wise provision of nature and a cause
of incredible furies and disasters. It is notorious that spaceship
crews are inordinately popular where colonies are small and strangers
infrequent. It is no less notorious that a girl may be destitute of
suitors on her own world, but has nearly her choice of husbands if she
merely saves the ship fare to another.

Calhoun could have predicted defiances of tradition and law and
quarantine alike, as soon as he began to learn the state of things
here. The frenzied rage produced by this specific case was normal.
Some young girl must have loved terribly, and some young man been no
less impassioned, to accept expulsion from society on a world where
there was no food except in hydroponic gardens and artificially warmed
pastures. It was no less than suicide for those who loved. It was no
less than a cause for battle among those who did not.

The deep-voiced Hunt said now, in leaden, heavy tones:

"Cap it. This is my doing. It was my daughter I did it for. I wanted to
keep her from dying. I'll pay for trying. They'll be satisfied in Three
City and in One alike if you tell 'em it's my fault and I've been drove
out for trouble-making."

Calhoun said sharply:

"What's that? What's going on now?"

The man in the shadows answered--by his tone as much to express disgust
as to give information.

"His daughter Nym was on sentry-duty against Three City sneaks. They
had a sentry against us. The two of 'em talked across the valley
between 'em. They had walkies to report with. They used 'em to talk.
Presently she sneaked a vision screen out of store. He prob'ly did,
too. So presently they figured it was worth dyin' to die together. They
run off for the hotlands. No chance to make it, o'course!"

The hotlands could hardly be anything but the warm equatorial belt of
the planet.

"We should've let them go on and die," said the stocky Hunt, drearily,
"but I persuaded men to help me bring 'em back. We were careful against
sickness! And we ... I ... locked them separate and I ... I hoped
my daughter mightn't die of the Three City sickness. I even hoped
that young man wouldn't die of the sickness they say we have that we
don't notice and they die of. Then we heard your call to One City. We
couldn't answer it, but we heard all you said, even to the bargain
about the cow. And ... we'd heard of Med men who cured sickness.
I ... hoped you could save Nym from dying of the Three City sickness
or passing it in our city. My friends risked much to bring you here.
But ... my daughter and the man have fled again."

"And nobody's goin' to risk any more!" rasped the voice from the shadow
of the cliff. "We held a council! It's decided! They're gone and we got
to burn out the places they was in! No more! You don't head the Council
any more, either! We decided that, too. And no Med man! The Council
ruled it!"

Calhoun nodded yet again. It is a part of fear, elaborately to ignore
everything that can be denied about the thing feared. Which includes
rational measures against it. This was a symptom of the state of things
which constituted a Med Service emergency, because it caused needless
deaths.

Hunt made a gesture which was at once commanding and filled with
despair.

"I'll take the Med man back so One City can use him if they dare and
not blame you for me taking him. I'll have to take the sledge--but he's
used it so it'd have to be burned anyhow. You men be sure to burn your
clothes. Three City'll be satisfied because I'm lost to balance for
their man lost. The Med man will tell One City I'm drove out. You've
lost me and my daughter too, and Three City's lost a man. One City'll
growl and threaten, but they win by this. They won't risk a showdown."

Silence again. As if reluctantly, one man of the party that had
abducted Calhoun moved away from the sledge and toward the abysmally
deep shadow of the cliff. Hunt said harshly:

"Don't forget to burn your clothes! You others, get off the sledge. I'm
taking the Med man back and there's no need for a war because I made
the mistake and I'm paying for it."

The remaining men of the kidnaping-party stepped off the sledge into
the trampled snow, just here. One said clumsily:

"Sorry, Hunt. Luck!"

"What luck could I have?" asked the stocky man, wearily.

       *       *       *       *       *

The roaring of the sledge's drive, which had been a mere muffled
throbbing, rose to a booming bellow. The snow-vehicle surged forward,
heading downward into the valley with the dark area below. Half a mile
down, it began to sweep in a great circle to return upon its former
track. Calhoun twisted in his seat and shouted above the roar. He
made violent gestures. The deep-voiced Hunt, driving from a standing
position behind the seat, slowed the sledge. It came nearly to a stop
and hissing noises from snow passing beneath it could be heard.

"What's the matter?" His tone was lifeless. "What d'you want?"

"Two people have run away," said Calhoun vexedly. "Your daughter Nym
and a man from Three City--whatever that is. You're driven out to
prevent fighting between the cities."

"Yes," said Hunt, without expression.

"Then let's go get the runaways," said Calhoun irritably, "before
they die in the snow! After all, you got me to have me save them! And
there's no need for anybody to die unless they have to!"

Hunt said without any expression at all:

"They're heading for the hotlands--where they'd never get. It's my
meaning to take you back to your ship, and then find them and give them
the sledge so's they'll ... so Nym will keep on living a while longer."

He moved to shift the controls and set the sledge again in motion. His
state of mind was familiar enough to Calhoun--shock or despair so great
that he could feel no other emotion. He would not react to argument.
He could not weigh it. He'd made a despairing conclusion and he was
lost to all thought beyond carrying it out. His intention was not
simply a violent reaction to a single event, such as an elopement. He
intended desperate means by which a complex situation could be kept
from becoming a catastrophe to others. Three City had to be dealt with
in this fashion, and One City in that, and it was requisite that he
die, himself. Not only for his daughter but for his community. He had
resolved to go to his death for good and sufficient reasons. To get his
attention to anything else, he would have to be shocked into something
other than despair.

Calhoun brought his hand out of its pocket. He held a blaster. He'd
pocketed the weapon before he went to examine the cow. He'd had the
power to stop his own abduction at any instant. But a medical man does
not refuse a call for professional service.

Now he pointed the blaster to one side and pressed the stud. A
half-acre of snow burst into steam. It bellowed upward and went
writhing away in the peculiar blue-gold glow of this world at night.

"I don't want to be taken back to my ship," said Calhoun firmly. "I
want to catch those runaways and do whatever's necessary so they won't
die at all. The situation here has been thrown into my lap. It's a
Med Service obligation to intervene in problems of public health, and
there's surely a public-health problem here!"

Murgatroyd wriggled vigorously under Calhoun's parka. He'd heard the
spitting of the blaster and the roaring of exploded steam. He was
disturbed. The stocky man stared.

"What's that?" he demanded blankly. "You pick up--"

"We're going to pick up your daughter and the man she's with," Calhoun
told him crossly. "There's an isolation syndrome and what looks like a
Crusoe problem here! It's got to be dealt with! As a matter of public
health!"

The stocky Hunt started at him. Calhoun's intentions were unimaginable
to him. He floundered among incredible ideas.

"We medics," said Calhoun, "made it necessary for men to invent
interplanetary travel because we kept people from dying and the
population on old Earth got too large. Then we made interstellar
travel necessary because we continued to keep people from dying and
one solar system wasn't big enough. We're responsible for nine-tenths
of civilization as it exists today, because we produced the conditions
that make civilization necessary! And since on this planet civilization
is going downhill and people are dying without necessity, I have the
plain obligation to stop it! So let's go pick up your daughter Nym and
this sweetheart of hers, and keep them from dying and get civilization
on the upgrade again!"

The former leader of the kidnapers said hoarsely:

"You mean--" Then he stammered. "Th-th-they're heading for the
hotlands. No other way to go. Watch for their tracks!"

       *       *       *       *       *

The drive-engine bellowed. The sledge raced ahead. And now it did not
complete the circle that had been begun, to head back to the landing
grid. Now it straightened and rushed in a splendid roaring fierceness
down between the sides of the valley. It left behind the dark patch
with its whirling mists. It flung aside bow-waves of fine snow, which
made rainbows in the half-light which was darkness here. It rushed and
rushed and rushed, leaving behind a depression which was a singular
permanent proof of its passage.

Calhoun cringed a little against the wind. He could see little or
nothing of what was ahead. The sprayed wings of upflung snow prevented
it. Hunt, standing erect, could do better. Murgatroyd, inside the
parka, again wriggled his nose out into the stinging wind and withdrew
it precipitately.

Hunt drove as if confident of where to go. Calhoun dourly began to fit
things into the standard pattern of how such things went. There were
self-evidently three cities or colonies on this planet. They'd been
named and he'd seen three patches of pasture from the stratosphere. One
was plainly warmed by power applied underground--electric power from
the landing grid's output. The one now falling behind was less likely
to be electrically heated. Steam seemed more probable because of the
vapor-veil above it. This sledge was surely fuel-powered. At a guess,
a ram-jet drove it. Such motors were simple enough to make, once the
principle of air inflow at low speeds was known. Two City--somewhere
to the rear--might operate on a fuel technology which could be based
on fossil oil or gas. The power-source for Three City could not now be
guessed.

Calhoun scowled as he tried to fill in the picture. His factual data
was still limited. There was the misty golden ribbon in space. It was
assuredly beyond the technical capacity of cities suffering from an
isolation syndrome. He'd guessed at hydroponic gardens underground.
There was surely no surface city near the landing grid, and the city
entrance they'd just left was in the face of a cliff. Such items
pointed to a limited technical capacity. Both, also, suggested mining
as the original purpose of the human colony or colonies here.

Only mining would make a colony self-supporting in an arctic climate.
This world could have been colonized to secure rare metals from it.
There could be a pipeline from an oil field or from a gas well field
near a landing grid. Local technological use of gas or oil to process
ores might produce ingots of rare metal worth interstellar freight
charges. One could even guess that metal reduced by heat-chemistry
could be transported in oil suspension over terrain and under
conditions when other forms of surface transportation were impractical.

If the colony began as a unit of that sort, it would require only very
occasional visits of spacecraft to carry away its products. It could
be a company-planet, colonized and maintained by a single interstellar
corporation. It could have been established a hundred and fifty or two
hundred years before, when the interstellar service organizations were
in their infancy and only operated where they were asked to serve. Such
a colony might not even be on record in the Medical Service files.

And that would account for everything. When for some reason the mines
became unprofitable, this colony would not be maintained. The people
who wished to leave would be taken off--of course. But some would
elect to stay behind in the warmed, familiar cities they and their
fathers had been born in. They couldn't imagine moving to a strange and
unfamiliar world.

So much was normal reasoning. Now the strictly technical logic of the
Med Service took over to explain the current state of things. In one
century or less an isolated community could lose, absolutely, its
defenses against diseases to which it was never exposed. Amerinds were
without defense against smallpox, back on Earth. A brown race scattered
among thousands of tiny islands was nearly wiped out by measles when
it was introduced. Any contact between a long-isolated community and
another--perhaps itself long-isolated--would bring out violently any
kind of contagion that might exist in either.

There was the mechanism of carriers. The real frequency of
disease-carriers in the human race had been established less than two
generations ago. A very small, isolated population could easily contain
a carrier or carriers of some infection. They could spread it so freely
that every member of their group acquired immunity during infancy.
But a different isolated group might contain a carrier of a different
infection and be immune but distributive of it.

It was literally true that each of the three cities might have
developed in their first century of isolation a separate immunity to
one disease and a separate defenselessness against all others. A member
of one community might be actually deadly to a member of either of the
others whom he met face to face.

With icy wind blowing upon him as the sledge rushed on, Calhoun wryly
realized that all this was wholly familiar. It was taught, nowadays,
that something of the sort had caused the ancient, primitive human
belief that women were perilous to men, and a man must exercise great
precaution to avoid evil _mana_ emanating from his prospective bride.
When wives were acquired by capture and all human communities were
small and fiercely self-isolated--why each unsanitary tribal group
might easily acquire a condition like that assumed in cities One, Two,
and Three. The primitive suspicion of woman would have its basis in
reality if the women of one tribe possessed immunity to some deadly
microbe their skin or garments harbored--and if their successful
abductors had no defense against it.

The speeding sledge swerved. It leaned inward against the turn. It
swerved again, throwing monstrous sheets of snow aloft. Then the
drive-jet lessened its roar. The shimmering bow-waves ceased. The
sledge slowed to a mere headlong glide.

"Their trail!" Hunt cried in Calhoun's ear.

Calhoun saw depressions in the snow. There were two sets of pear-shaped
dents in the otherwise virgin surface. Two man beings, wearing oblong
frames on their feet, criss-crossed with cordage to support them atop
the snow, had trudged ahead, here, through the gold-blue night.

       *       *       *       *       *

Calhoun knew exactly what had happened. He could make the modifications
the local situation imposed upon a standard pattern, and reconstitute a
complete experience leading up to now.

A girl in heavy, clumsy garments had mounted guard in a Two City
sentry-post above a snow-filled mountain valley. There were long and
bitter-cold hours of watching, in which nothing whatever happened.
Eternal snows seemed eternally the same, and there was little in life
but monotony. But she'd known that across the valley there was another
lonely watcher from an alien city, the touch of whose hand or even
whose breath would mean sickness and death. She'd have mused upon the
strangeness that protected her in this loneliness--because her touch
or her breath would be contagion upon him, too. She'd have begun by
feeling a vague dread of the other sentry. But presently, perhaps,
there came a furtive call on the walkie-frequency used by sentries for
communication with their own cities.

Very probably she did not answer at first. But she might listen. And
she would hear a young man's voice, filled with curiosity about the
sentry who watched as he did.

There'd come a day when she'd answer shyly. And there would be
relief and a certain fascination in talking to someone so much like
herself--but so alien and so deadly! Of course there could be no harm
in talking to someone who would flee from actual face-to-face contact
as desperately as herself. They might come to joke about their mutual
dangerousness. They might find it amusing that cities which dared not
meet should hate. Then there'd come a vast curiosity to see each other.
They'd discuss that frankly--because what possible evil could come, if
two persons were deadly to each other should they actually approach?

Then there'd come a time when they looked at each other breathlessly
in vision-screens they'd secretly stolen from their separate cities'
stores. There could be no harm. They were only curious! But she would
see someone at once infinitely strange but utterly dear, and he would
see someone lovely beyond the girls of his own city. Then they would
regret the alienness which made them perilous to each other. Then they
would resent it fiercely. They'd end by denying it.

So across the wide valley of eternal snow there would travel whispers
of desperate rebellion, and then firmly resolute murmurings, and then
what seemed the most obvious of truths--that it would be much more
satisfactory to die together than to live apart. And insane plannings
would follow--arrangements by which two trembling young folk would meet
secretly and flee. Toward the hotlands, to be sure, but without any
belief than that the days before death, while they were together, were
more precious than the lifetimes they would give up to secure them.

Calhoun could see all this very clearly, and he assured himself that he
regarded it with ironic detachment. He asserted in his own mind that
it was merely the manifestation of that blind impulse to exogamy which
makes spacemen romantic in far spaceports and invests an outer-planet
girl with glamour. But it was something more. It was also that strange
and unreasonable and solely human trait which causes one to rejoice
selflessly that someone else exists, so that his or her own life and
happiness is put into its place of proper insignificance in the cosmos.
It may begin in instinct, but it becomes an achievement only humans can
encompass.

Hunt knew it--the stocky, deep-voiced despairing figure who stared
hungrily for the daughter who had defied him and for whom he was an
exile from all food and warmth.

He flung out a mittened hand.

"There!" he cried joyously. "It's them!"

There was a dark speck in the blue-gold night-glow. As the sledge swept
close, there were two small figures who stood close together. They
defiantly faced the approaching sledge. As its drive-motor stopped
and it merely glided on, its runners whispering on the snow, the girl
snatched away the cold-mask which all the inhabitants of this planet
wore out-of-doors. She raised her face to the man. They kissed.

And then the young man desperately raised a knife. It glittered in the
light of the ribbon in the sky. And--

Calhoun's blaster made its inadequate rasping noise. The knife-blade
turned incandescent for two-thirds of its length. The young man dropped
the suddenly searing handle. The knife sank hissing into the snow.

"It's always thrilling to be dramatic," said Calhoun severely, "but I
assure you it's much more satisfying to be sane. The young lady's name
is Nym, I believe. I do not know the gentleman. But Nym's father and
myself have come to put the technical resources of two civilizations
at your disposal as a first step toward treatment of the pandemic
isolation syndrome on this planet, which with the complications that
have developed amounts to a Crusoe health problem."

Murgatroyd tried feverishly to get his head out of Calhoun's parka
past his chin. He'd heard a blaster. He sensed excitement. His nose
emerged, whiffing frantically. Calhoun pushed it back.

"Tell them, Hunt," he said irritably. "Tell them what we're here for
and what you've done already!"

The girl's father told her unsteadily--almost humbly, for some
reason--that the jet-sledge had come to take her and her sweetheart--to
be her husband--to the hotlands where at least they would not die of
cold. Calhoun added crossly that he believed there would even be food
there--because of the ribbon in the sky.

Trembling and abashed, the fugitives got on the sledge. Its motor
roared. It surged toward the hotlands under the golden glow of that
ribbon--which obviously had no rational explanation unless somebody had
made a grave mistake. But Calhoun had not.




                                  IV


    "An action is normally the result of a thought. Since we cannot
    retract an action, we tend to feel that we cannot retract the
    thought which produced it. In effect, we cling desperately to our
    mistakes. In order to change our views we have commonly to be
    forced to act upon new thoughts, so urgent and so necessary that
    without disowning our former, mistaken ideas, we can abandon them
    tactfully without saying anything to anybody--even ourselves."

                                             _The Practice of Thinking_
                                                             Fitzgerald


Murgatroyd came down a tree with his cheek-pouches bulged with nuts.
Calhoun inserted a finger, and Murgatroyd readily permitted him to
remove and examine the results of his scramble aloft. Calhoun grunted.
Murgatroyd did have other and more useful abilities in the service
of public health, but right here and now his delicate digestion was
extremely convenient. His stomach worked so much like a human's, that
anything Murgatroyd ate was safe for Calhoun to an incredible degree of
probability. And Murgatroyd ate nothing that disagreed with him.

"Instead of 'physician, heal thyself,'" Calhoun observed, "it's
amounted to 'physician, feed thyself,' since we got past the
frost-line, Murgatroyd. I am gratified."

"_Chee!_" said Murgatroyd complacently.

"I expected," said Calhoun, "only to benefit by the charm of your
society in what I thought would be a routine check-trip to Merida Two.
Instead, some unknown fumble-finger punched a wrong button and we wound
up here. Not exactly here, but near enough. I brought you from the Med
Ship because there was nobody to stay around and feed you, and now you
feed us--at least by pointing out edible things we might otherwise
miss."

"_Chee!_" said Murgatroyd. He strutted.

"I wish," protested Calhoun annoyedly, "that you wouldn't imitate that
Pat character from Three City! As a brand-new husband he's entitled to
strut a little, but I object to your imitating him! You haven't anybody
acting like Nym!--gazing at you raptly as if you'd invented not only
marriage but romance itself, impassioned falsehoods, and all other
desirable things back to night and morning!"

Murgatroyd said, "_Chee?_" and turned to face away from Calhoun.

The two of them, just then, stood on a leaf-covered patch of ground
which slanted down to the singularly smooth and reflective water of
a tiny bay. Behind and above them reared gigantic mountains. There
was snow in blinding-white sheets overhead, but the snowline itself
was safely three thousand feet above them. Beyond the bay was a wide
estuary, with more mountains behind it, with more snowfields on their
flanks. A series of leaping cascades jumped downward from somewhere
aloft where a glacier-foot melted in the sun's heat. And everywhere
that snow was not, green stuff shone in the sunlight.

Nym's father, Hunt, came hurriedly toward the pair. He'd abandoned the
thick felt cloak and heavy boots of Two City. Now he was dressed nearly
like a civilized man, but he carried a sharpened stick in one hand
and in the other a string of authentic fish. He wore an expression of
astonishment. It was becoming habitual.

"Murgatroyd," said Calhoun casually, "has found another kind of edible
nut. Terrestrial, too, like half the living things we've seen. Only the
stuff crowding the glaciers seems to be native. The rest originated on
Earth and was brought here, some time or another."

Hunt nodded. He seemed to find some difficulty in speaking.

"I've been talking to Pat," he said at last.

"The son-in-law," observed Calhoun, "who has to thank you not only for
your daughter and his life, but for your public career in Two City
which qualified you to perform a marriage ceremony. I hope he was
respectful."

Hunt made an impatient gesture.

"He says," he protested, "that you haven't done anything either to Nym
or to him to keep them from dying!"

Calhoun nodded.

"That's true."

"But ... they should die! Nym should die of the Three City sickness!
And Three City people have always said that we had a sickness too ...
that did not harm us but they died of!"

"Which," agreed Calhoun, "is undoubtedly historical fact. Its current
value is that of one factor in an isolation syndrome and consequently
a complicating factor in the Crusoe health problem here. I've let Nym
and Pat go untreated to prove it. I think there's only a sort of mass
hypochondria based on strictly accurate tradition. Which would be
normal."

Hunt shook his head.

"I don't understand!" he protested helplessly.

"Someday I'll draw a diagram," Calhoun told him. "It is complicated.
Did you check with Pat on what Three City knows about the ribbon in the
sky? I suspect it accounts for the terrestrial plants and animals here,
indirectly. There wouldn't be an accidental planting of edible nuts and
fish and squirrels and pigeons and rabbits and bumblebees! I suspect
there was a mistake somewhere. What does Pat say?"

Hunt shrugged his shoulders.

"When I talk to him," added Calhoun, "he doesn't pay attention.
He simply gazes at Nym and beams. The man's mad! But you're his
father-in-law. He has to be polite to you!"

       *       *       *       *       *

Hunt sat down abruptly. He rested his spear against a tree and
looked over his string of fish. He wasn't used to the abundance of
foodstuffs here, and the temperature--Calhoun estimated it at fifty
degrees--seemed to him incredibly balmy. Now he thoughtfully separated
one fish from the rest and with a certain new skill began to slice away
two neatly boneless fillets. Calhoun had showed him the trick the day
after a lesson in fish-spearing, which was two days after their arrival.

"Children in Three City," growled Hunt, "are taught the same as in Two
City. Men came to this planet to work the mines. There was a company
which sent them, and every so often it sent ships to take what the
mines yielded, and to bring things the people wanted. Men lived well
and happily. The company hung the ribbon in the sky so the hotlands
could grow food for the men. But presently the mines could not deliver
what they made to the ships when they came. The hotlands grew bigger,
the glaciers flowed faster, and the pipes between the cities were
broken and could not be kept repaired. So the company said that since
the mine-products could no longer be had, it could not send the ships.
Those who wanted to move to other worlds would be carried there. Some
men went, with their wives and children. But the grandfathers of our
fathers' grandfathers were contented here. They had homes and heat and
food. They would not go."

Hunt regarded the pinkish brook trout fillet he'd just separated. He
bit off a mouthful and chewed, thoughtfully.

"That really tastes better cooked," said Calhoun mildly.

"But it is good this way also," said Hunt. He was grizzled and stocky
and somehow possessed of dignity which was not to be lost merely by
eating raw fish. He waved the remainder of the fillet. "Then the ships
ceased to come. Then sickness came. One City had a sickness it gave to
people of Two and Three when they visited it. Two City had a sickness
it gave to One and Three. Three City--" He grunted. "Our children in
Two say only Two City people have no sickness. Three City children are
taught that only Three City is clean of sickness."

Calhoun said nothing. Murgatroyd tried to gnaw open one of the nuts
he'd brought down from the tree. Calhoun took it and another and struck
them together. Both cracked. He gave them to Murgatroyd, who ate them
with great satisfaction.

Hunt looked up suddenly.

"Pat did not give a Three City sickness to Nym," he observed, "so our
thinking was wrong. And Nym has not given a Two City sickness to him.
His thinking was wrong."

Calhoun said meditatively:

"It's tricky. But sickness can be kept by a carrier, just as you people
have believed of other cities. A carrier has a sickness but does not
know it. People around the carrier have the sickness on their bodies
or their clothing from the carrier. They distribute it. Soon everybody
in the city where there is a carrier--" Calhoun had a moment's qualm
because he used the word "city." But to Hunt the idea conveyed was a
bare few hundred people. "Soon everybody is used to the sickness. They
are immune. They cannot know it. But somebody from another city can
come, and they are not used to the sickness, and they become ill and
die."

Hunt considered shrewdly.

"Because the sickness is on clothing? From the carrier?"

Calhoun nodded.

"Different carriers have different sicknesses. So one carrier in One
City might have one disease, and all the people in One City became
used to it while they were babies--became immune. There could be
another carrier with another sickness in Two City. A third in Three
City. In each city they were used to their own sickness--"

"That is it," said Hunt, nodding. "But why is Pat not dying? Or Nym?
Why do you do nothing to keep them alive?"

"Suppose," said Calhoun, "the carrier of a sickness dies. What happens?"

Hunt bit again, and chewed. Suddenly he choked. He sputtered:

"There is no sickness to spread on the clothing! The people no longer
have it to give to strangers who are not used to it! The babies do not
get used to it while they are little! There is no longer a One City
sickness or a Two City sickness or a Three!"

"There is," said Calhoun, "only a profound belief in them. You had it.
Everybody else still has it. And the cities are isolated and put out
sentries because they believe in what used to be true. And people like
Nym and Pat run away in the snow and die of it. There is much death
because of it. You would have died of it."

Hunt chewed and swallowed. Then he grinned.

"Now what?" His deep voice was quaintly respectful to Calhoun, so much
younger than himself. "I like this! We were not fools to believe,
because it was true. But we are fools if we still believe, because it
is not true any more. How do we make people understand, Calhoun? You
tell me. I can handle people when they are not afraid. I can make them
do what I think wise--when they are not afraid. But when they fear--"

"When they fear," said Calhoun dryly, "they want a stranger to tell
them what to do. You came for me, remember? You are a stranger to One
City and Three City. Pat is a Stranger to Two City. If the cities
become really afraid--"

       *       *       *       *       *

Hunt grunted. He watched Calhoun intently. And Calhoun was peculiarly
reminded of the elected president of a highly cultured planet, who had
exactly that completely intent way of looking at one.

"Go on!" said Hunt. "How frighten them into--this?"

He waved his hand about. Calhoun, his tone very dry indeed, told him.
Words would not be enough. Threats would not be enough. Promises would
not be enough. But rabbits and pigeons and squirrels and fish--fish
that were frozen like other human food--and piles of edible nuts....
They would not be enough either, by themselves. But--

"An isolation syndrome is a neurotic condition, and a Crusoe problem
amounts to neurotic hypochondria. You can do it--you and Pat."

Hunt grimaced.

"I hate the cold, now. But I will do it. After all, if I am to have
grandchildren there should be other children for them to play with!
And we will take you back to your ship?"

"You will," said Calhoun. "By the way, what is the name of this planet,
anyhow?"

Hunt told him.

       *       *       *       *       *

Calhoun slipped across the pasture inside the landing grid and examined
the ship from the outside. There had been batterings, but the door
had not been opened. In the light of the ribbon in the sky he could
see, too, that the ground was trampled down but only at a respectful
distance. One City was disturbed about the Med Ship. But it did not
know what to do. So long as nothing happened from it....

He was working the combination lock-door when something hopped,
low-down and near him. He jumped, and Murgatroyd said, "_Chee?_" Then
Calhoun realized what had startled him. He finished the unlocking of
the port. He went in and closed the port behind him. The air inside
seemed curiously dead, after so long a time outside. He flipped on
the outside microphones and heard tiny patterings. He heard mildly
resentful cooings. He grinned.

When morning came, the people of One City would find their pastureland
inhabited by small snowshoe rabbits and small and bush-tailed squirrels
and fluttering pigeons. They would react as Two City and Three City had
already done--with panic. And panic would inevitably call up the notion
of the most-feared thing in their lives. Sickness. The most-feared
thing is always a rare thing, of course. One cannot fear a frequent
thing, because one either dies of it or comes to take it for granted.
Fear is always of the rare or nonexistent. One City would be filled
with fear of sickness.

And sickness would come. Hunt would call them, presently, on a
walkie-talkie communicator. He would express deep concern because--so
he'd say--new domestic animals intended for Two City had been dumped
on One City pastureland. He'd add that they were highly infective, and
Two City was already inescapably doomed to an epidemic which would
begin with severe headaches, and would continue with cramps and extreme
nervous agitation. And he would say that Calhoun had left medicines at
Two City with which that sickness and all others could be cured, and
if the sickness described should appear in One City--why--its victims
could be cured if they traveled to Two City.

The sickness would appear. Inevitably. There was no longer sickness in
the three communities. Arctic colonies, never visited by people from
reservoirs of infection, become magnificently healthy by the operation
of purely natural causes. But an isolation syndrome....

The people of One City would presently travel, groaning, to Two City.
Their suffering would be real. They would dread the breaking of
their isolation. But they'd dread sickness--even sickness they only
imagined--still more. And when they reached Two City they would find
themselves tended by Three City members, and they would be appalled
and terrified. But mumbo-jumbo medication by Hunt and Pat--and Nym for
the women--would reassure them. A Crusoe condition requires heroic
treatment. This was it.

       *       *       *       *       *

Calhoun cheerfully checked over the equipment of the Med Ship. He'd
have to take off on emergency rockets. He'd have to be very, very
careful in setting a course back to Headquarters to report before
starting out again for Merida II. He didn't want to make any mistakes.
Suddenly he began to chuckle.

"Murgatroyd," he said amiably, "it's just occurred to me that the
mistakes we make--that we struggle so hard to avoid--are part of the
scheme of things."

"_Chee?_" said Murgatroyd inquiringly.

"The company that settled this planet," said Calhoun, grinning, "set
up that ribbon out in space as a splendidly conservative investment
to save money in freight charges. It was a mistake, because it ruined
their mining business and they had to write the whole colony off.
They made another mistake by not reporting to Med Service, because
now they've abandoned the colony and would have to get a license to
re-occupy--which they'd never be granted against the population already
there. Somebody made a mistake that brought us here, and One City made
a mistake by not accepting us as guests, and Two City made a mistake by
sending Nym on sentry-duty, and Three City made a mistake...."

Murgatroyd yawned.

"You," said Calhoun severely, "make a mistake in not paying attention."
He strapped himself in. He stabbed an emergency-rocket control-button.
The little ship shot heavenward on a pencil-thin stream of fire.
Below him, people of One City would come pouring out of underground
to learn what had happened, and they'd find the pasture swarming with
friendly squirrels and inquisitive rabbits and cooing pigeons. They'd
be scared to death. Calhoun laughed. "I'll spend part of the time in
overdrive making a report on it. Since an isolation syndrome is mostly
psychological, and a Crusoe condition is wholly so--I managed sound
medical treatment by purely psychological means! I'll have fun with
that!"

It was a mistake. He got back to Headquarters all right, but when his
report was read they made him expand it into a book, with footnotes, an
index, and a bibliography.

It was very much of a mistake!


                                THE END