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                                DOCTOR

                          BY MURRAY LEINSTER

                         Illustrated by FINLAY

           [Transcriber's Note: This etext was produced from
                    Galaxy Magazine February 1961.
         Extensive research did not uncover any evidence that
         the U.S. copyright on this publication was renewed.]




                   Suddenly the biggest thing in the
                    universe was the very tiniest.


There were suns, which were nearby, and there were stars which were
so far away that no way of telling their distance had any meaning.
The suns had planets, most of which did not matter, but the ones that
did count had seas and continents, and the continents had cities and
highways and spaceports. And people.

The people paid no attention to their insignificance. They built ships
which went through emptiness beyond imagining, and they landed upon
planets and rebuilt them to their own liking. Suns flamed terribly,
renting their impertinence, and storms swept across the planets
they preëmpted, but the people built more strongly and were secure.
Everything in the universe was bigger or stronger than the people,
but they ignored the fact. They went about the businesses they had
contrived for themselves.

They were not afraid of anything until somewhere on a certain small
planet an infinitesimal single molecule changed itself.

It was one molecule among unthinkably many, upon one planet of one
solar system among uncountable star clusters. It was not exactly alive,
but it acted as if it were, in which it was like all the important
matter of the cosmos. It was actually a combination of two complicated
substances not too firmly joined together. When one of the parts
changed, it became a new molecule. But, like the original one, it was
still capable of a process called autocatalysis. It practiced that
process and catalyzed other molecules into existence, which in each
case were duplicates of itself. Then mankind had to take notice, though
it ignored flaming suns and monstrous storms and emptiness past belief.

Men called the new molecule a virus and gave it a name. They called it
and its duplicates "chlorophage." And chlorophage was, to people, the
most terrifying thing in the universe.

       *       *       *       *       *

In a strictly temporary orbit around the planet Altaira, the _Star
Queen_ floated, while lift-ships brought passengers and cargo up to
it. The ship was too large to be landed economically at an unimportant
spaceport like Altaira. It was a very modern ship and it made the
Regulus-to-Cassim run, which is five hundred light-years, in only fifty
days of Earthtime.

Now the lift-ships were busy. There was an unusual number of passengers
to board the _Star Queen_ at Altaira and an unusual number of them were
women and children. The children tended to pudginess and the women had
the dieted look of the wives of well-to-do men. Most of them looked
red-eyed, as if they had been crying.

One by one the lift-ships hooked onto the airlock of the _Star Queen_
and delivered passengers and cargo to the ship. Presently the last of
them was hooked on, and the last batch of passengers came through to
the liner, and the ship's doctor watched them stream past him.

His air was negligent, but he was actually impatient. Like most
doctors, Nordenfeld approved of lean children and wiry women. They had
fewer things wrong with them and they responded better to treatment.
Well, he was the doctor of the _Star Queen_ and he had much authority.
He'd exerted it back on Regulus to insist that a shipment of botanical
specimens for Cassim travel in quarantine--to be exact, in the ship's
practically unused hospital compartment--and he was prepared to
exercise authority over the passengers.

He had a sheaf of health slips from the examiners on the ground below.
There was one slip for each passenger. It certified that so-and-so had
been examined and could safely be admitted to the _Star Queen's_ air,
her four restaurants, her two swimming pools, her recreation areas and
the six levels of passenger cabins the ship contained.

He impatiently watched the people go by. Health slips or no health
slips, he looked them over. A characteristic gait or a typical
complexion tint, or even a certain lack of hair luster, could tell him
things that ground physicians might miss. In such a case the passenger
would go back down again. It was not desirable to have deaths on a
liner in space. Of course nobody was ever refused passage because of
chlorophage. If it were ever discovered, the discovery would already be
too late. But the health regulations for space travel were very, very
strict.

He looked twice at a young woman as she passed. Despite applied
complexion, there was a trace of waxiness in her skin. Nordenfeld had
never actually seen a case of chlorophage. No doctor alive ever had.
The best authorities were those who'd been in Patrol ships during the
quarantine of Kamerun when chlorophage was loose on that planet. They'd
seen beamed-up pictures of patients, but not patients themselves. The
Patrol ships stayed in orbit while the planet died. Most doctors, and
Nordenfeld was among them, had only seen pictures of the screens which
showed the patients.

       *       *       *       *       *

He looked sharply at the young woman. Then he glanced at her hands.
They were normal. The young woman went on, unaware that for the
fraction of an instant there had been the possibility of the landing of
the _Star Queen_ on Altaira, and the destruction of her space drive,
and the establishment of a quarantine which, if justified, would mean
that nobody could ever leave Altaira again, but must wait there to die.
Which would not be a long wait.

A fat man puffed past. The gravity on Altaira was some five per cent
under ship-normal and he felt the difference at once. But the veins at
his temples were ungorged. Nordenfeld let him go by.

There appeared a white-haired, space-tanned man with a briefcase under
his arm. He saw Nordenfeld and lifted a hand in greeting. The doctor
knew him. He stepped aside from the passengers and stood there. His
name was Jensen, and he represented a fund which invested the surplus
money of insurance companies. He traveled a great deal to check on the
business interests of that organization.

The doctor grunted, "What're you doing here? I thought you'd be on the
far side of the cluster."

"Oh, I get about," said Jensen. His manner was not quite normal. He was
tense. "I got here two weeks ago on a Q-and-C tramp from Regulus. We
were a ship load of salt meat. There's romance for you! Salt meat by
the spaceship load!"

The doctor grunted again. All sorts of things moved through space,
naturally. The _Star Queen_ carried a botanical collection for a museum
and pig-beryllium and furs and enzymes and a list of items no man could
remember. He watched the passengers go by, automatically counting them
against the number of health slips in his hand.

"Lots of passengers this trip," said Jensen.

"Yes," said the doctor, watching a man with a limp. "Why?"

Jensen shrugged and did not answer. He was uneasy, the doctor noted.
He and Jensen were as much unlike as two men could very well be, but
Jensen was good company. A ship's doctor does not have much congenial
society.

The file of passengers ended abruptly. There was no one in the _Star
Queen's_ airlock, but the "Connected" lights still burned and the
doctor could look through into the small lift-ship from the planet down
below. He frowned. He fingered the sheaf of papers.

"Unless I missed count," he said annoyedly, "there's supposed to be one
more passenger. I don't see--"

A door opened far back in the lift-ship. A small figure appeared. It
was a little girl perhaps ten years old. She was very neatly dressed,
though not quite the way a mother would have done it. She wore the
carefully composed expression of a child with no adult in charge of
her. She walked precisely from the lift-ship into the _Star Queen's_
lock. The opening closed briskly behind her. There was the rumbling of
seals making themselves tight. The lights flickered for "Disconnect"
and then "All Clear." They went out, and the lift-ship had pulled away
from the _Star Queen_.

"There's my missing passenger," said the doctor.

       *       *       *       *       *

The child looked soberly about. She saw him. "Excuse me," she said very
politely. "Is this the way I'm supposed to go?"

"Through that door," said the doctor gruffly.

"Thank you," said the little girl. She followed his direction. She
vanished through the door. It closed.

There came a deep, droning sound, which was the interplanetary drive
of the _Star Queen_, building up that directional stress in space
which had seemed such a triumph when it was first contrived. The ship
swung gently. It would be turning out from orbit around Altaira. It
swung again. The doctor knew that its astrogators were feeling for the
incredibly exact pointing of its nose toward the next port which modern
commercial ship operation required. An error of fractional seconds of
arc would mean valuable time lost in making port some ten light-years
of distance away. The drive droned and droned, building up velocity
while the ship's aiming was refined and re-refined.

The drive cut off abruptly. Jensen turned white.

The doctor said impatiently, "There's nothing wrong. Probably a message
or a report should have been beamed down to the planet and somebody
forgot. We'll go on in a minute."

But Jensen stood frozen. He was very pale. The interplanetary drive
stayed off. Thirty seconds. A minute. Jensen swallowed audibly. Two
minutes. Three.

The steady, monotonous drone began again. It continued interminably, as
if while it was off the ship's head had swung wide of its destination
and the whole business of lining up for a jump in overdrive had to be
done all over again.

Then there came that "Ping-g-g-g!" and the sensation of spiral fall
which meant overdrive. The droning ceased.

Jensen breathed again. The ship's doctor looked at him sharply. Jensen
had been taut. Now the tensions had left his body, but he looked as
if he were going to shiver. Instead, he mopped a suddenly streaming
forehead.

"I think," said Jensen in a strange voice, "that I'll have a drink. Or
several. Will you join me?"

Nordenfeld searched his face. A ship's doctor has many duties in
space. Passengers can have many things wrong with them, and in the
absolute isolation of overdrive they can be remarkably affected by each
other.

"I'll be at the fourth-level bar in twenty minutes," said Nordenfeld.
"Can you wait that long?"

"I probably won't wait to have a drink," said Jensen. "But I'll be
there."

The doctor nodded curtly. He went away. He made no guesses, though he'd
just observed the new passengers carefully and was fully aware of the
strict health regulations that affect space travel. As a physician he
knew that the most deadly thing in the universe was chlorophage and
that the planet Kamerun was only one solar system away. It had been
a stop for the _Star Queen_ until four years ago. He puzzled over
Jensen's tenseness and the relief he'd displayed when the overdrive
field came on. But he didn't guess. Chlorophage didn't enter his mind.

Not until later.

       *       *       *       *       *

He saw the little girl who'd come out of the airlock last of all the
passengers. She sat on a sofa as if someone had told her to wait there
until something or other was arranged. Doctor Nordenfeld barely glanced
at her. He'd known Jensen for a considerable time. Jensen had been
a passenger on the _Star Queen_ half a dozen times, and he shouldn't
have been upset by the temporary stoppage of an interplanetary drive.
Nordenfeld divided people into two classes, those who were not and
those who were worth talking to. There weren't many of the latter.
Jensen was.

He filed away the health slips. Then, thinking of Jensen's pallor,
he asked what had happened to make the _Star Queen_ interrupt her
slow-speed drive away from orbit around Altaira.

The purser told him. But the purser was fussily concerned because there
were so many extra passengers from Altaira. He might not be able to
take on the expected number of passengers at the next stop-over point.
It would be bad business to have to refuse passengers! It would give
the space line a bad name.

Then the air officer stopped Nordenfeld as he was about to join Jensen
in the fourth-level bar. It was time for a medical inspection of the
quarter-acre of Banthyan jungle which purified and renewed the air
of the ship. Nordenfeld was expected to check the complex ecological
system of the air room. Specifically, he was expected to look for and
identify any patches of colorlessness appearing on the foliage of the
jungle plants the _Star Queen_ carried through space.

The air officer was discreet and Nordenfeld was silent about the
ultimate reason for the inspection. Nobody liked to think about it. But
if a particular kind of bleaching appeared, as if the chlorophyll of
the leaves were being devoured by something too small to be seen by an
optical microscope--why, that would be chlorophage. It would also be a
death sentence for the _Star Queen_ and everybody in her.

But the jungle passed medical inspection. The plants grew lushly in
soil which periodically was flushed with hydroponic solution and
then drained away again. The UV lamps were properly distributed and
the different quarters of the air room were alternately lighted and
darkened. And there were no colorless patches. A steady wind blew
through the air room and had its excess moisture and unpleasing smells
wrung out before it recirculated through the ship. Doctor Nordenfeld
authorized the trimming of some liana-like growths which were
developing woody tissue at the expense of leaves.

The air officer also told him about the reason for the turning off of
the interplanetary drive. He considered it a very curious happening.

The doctor left the air room and passed the place where the little
girl--the last passenger to board the _Star Queen_--waited patiently
for somebody to arrange something. Doctor Nordenfeld took a lift to the
fourth level and went into the bar where Jensen should be waiting.

He was. He had an empty glass before him. Nordenfeld sat down and
dialed for a drink. He had an indefinite feeling that something was
wrong, but he couldn't put his finger on it. There are always things
going wrong for a ship's doctor, though. There are so many demands on
his patience that he is usually short of it.

Jensen watched him sip at his drink.

"A bad day?" he asked. He'd gotten over his own tension.

       *       *       *       *       *

Nordenfeld shrugged, but his scowl deepened. "There are a lot of new
passengers." He realized that he was trying to explain his feelings to
himself. "They'll come to me feeling miserable. I have to tell each one
that if they feel heavy and depressed, it may be the gravity-constant
of the ship, which is greater than their home planet. If they feel
light-headed and giddy, it may be because the gravity-constant of
the ship is less than they're used to. But it doesn't make them feel
better, so they come back for a second assurance. I'll be overwhelmed
with such complaints within two hours."

Jensen waited. Then he said casually--too casually, "Does anybody ever
suspect chlorophage?"

"No," said Nordenfeld shortly.

Jensen fidgeted. He sipped. Then he said, "What's the news from
Kamerun, anyhow?"

"There isn't any," said Nordenfeld. "Naturally! Why ask?"

"I just wondered," said Jensen. After a moment: "What was the last
news?"

"There hasn't been a message from Kamerun in two years," said
Nordenfeld curtly. "There's no sign of anything green anywhere on the
planet. It's considered to be--uninhabited."

Jensen licked his lips. "That's what I understood. Yes."

Nordenfeld drank half his drink and said unpleasantly, "There were
thirty million people on Kamerun when the chlorophage appeared. At
first it was apparently a virus which fed on the chlorophyll of
plants. They died. Then it was discovered that it could also feed on
hemoglobin, which is chemically close to chlorophyll. Hemoglobin is the
red coloring matter of the blood. When the virus consumed it, people
began to die. Kamerun doctors found that the chlorophage virus was
transmitted by contact, by inhalation, by ingestion. It traveled as
dust particles and on the feet of insects, and it was in drinking water
and the air one breathed. The doctors on Kamerun warned spaceships
off and the Patrol put a quarantine fleet in orbit around it to keep
anybody from leaving. And nobody left. And everybody died. _And_ so did
every living thing that had chlorophyll in its leaves or hemoglobin in
its blood, or that needed plant or animal tissues to feed on. There's
not a person left alive on Kamerun, nor an animal or bird or insect,
nor a fish nor a tree, or plant or weed or blade of grass. There's no
longer a quarantine fleet there. Nobody'll go there and there's nobody
left to leave. But there are beacon satellites to record any calls and
to warn any fool against landing. If the chlorophage got loose and was
carried about by spaceships, it could kill the other forty billion
humans in the galaxy, together with every green plant or animal with
hemoglobin in its blood."

"That," said Jensen, and tried to smile, "sounds final."

"It isn't," Nordenfeld told him. "If there's something in the
universe which can kill every living thing except its maker, that
something should be killed. There should be research going on about
the chlorophage. It would be deadly dangerous work, but it should be
done. A quarantine won't stop contagion. It can only hinder it. That's
useful, but not enough."

Jensen moistened his lips.

Nordenfeld said abruptly, "I've answered your questions. Now what's on
your mind and what has it to do with chlorophage?"

Jensen started. He went very pale.

"It's too late to do anything about it," said Nordenfeld. "It's
probably nonsense anyhow. But what is it?"

Jensen stammered out his story. It explained why there were so many
passengers for the _Star Queen_. It even explained his departure from
Altaira. But it was only a rumor--the kind of rumor that starts up
untraceably and can never be verified. This one was officially denied
by the Altairan planetary government. But it was widely believed by the
sort of people who usually were well-informed. Those who could sent
their families up to the _Star Queen_. And that was why Jensen had been
tense and worried until the liner had actually left Altaira behind.
Then he felt safe.

Nordenfeld's jaw set as Jensen told his tale. He made no comment, but
when Jensen was through he nodded and went away, leaving his drink
unfinished. Jensen couldn't see his face; it was hard as granite.

And Nordenfeld, the ship's doctor of the _Star Queen_, went into the
nearest bathroom and was violently sick. It was a reaction to what he'd
just learned.

       *       *       *       *       *

There were stars which were so far away that their distance didn't
mean anything. There were planets beyond counting in a single star
cluster, let alone the galaxy. There were comets and gas clouds in
space, and worlds where there was life, and other worlds where life was
impossible. The quantity of matter which was associated with life was
infinitesimal, and the quantity associated with consciousness--animal
life--was so much less that the difference couldn't be expressed.
But the amount of animal life which could reason was so minute by
comparison that the nearest ratio would be that of a single atom to
a sun. Mankind, in fact, was the least impressive fraction of the
smallest category of substance in the galaxy.

But men did curious things.

There was the cutting off of the _Star Queen's_ short-distance drive
before she'd gotten well away from Altaira. There had been a lift-ship
locked to the liner's passenger airlock. When the last passenger
entered the big ship--a little girl--the airlocks disconnected and the
lift-ship pulled swiftly away.

It was not quite two miles from the _Star Queen_ when its emergency
airlocks opened and spacesuited figures plunged out of it to emptiness.
Simultaneously, the ports of the lift-ship glowed and almost
immediately the whole plating turned cherry-red, crimson, and then
orange, from unlimited heat developed within it.

The lift-ship went incandescent and ruptured and there was a spout
of white-hot air, and then it turned blue-white and puffed itself to
nothing in metallic steam. Where it had been there was only shining
gas, which cooled. Beyond it there were figures in spacesuits which
tried to swim away from it.

The _Star Queen's_ control room, obviously, saw the happening. The
lift-ship's atomic pile had flared out of control and melted down the
ship. It had developed something like sixty thousand degrees Fahrenheit
when it ceased to flare. It did not blow up; it only vaporized. But
the process must have begun within seconds after the lift-ship broke
contact with the _Star Queen_.

In automatic reaction, the man in control of the liner cut her drive
and offered to turn back and pick up the spacesuited figures in
emptiness. The offer was declined with almost hysterical haste. In
fact, it was barely made before the other lift-ships moved in on rescue
missions. They had waited. And they were picking up castaways before
the _Star Queen_ resumed its merely interplanetary drive and the
process of aiming for a solar system some thirty light-years away.

When the liner flicked into overdrive, more than half the floating
figures had been recovered, which was remarkable. It was almost as
remarkable as the flare-up of the lift-ship's atomic pile. One has
to know exactly what to do to make a properly designed atomic pile
vaporize metal. Somebody had known. Somebody had done it. And the other
lift-ships were waiting to pick up the destroyed lift-ship's crew when
it happened.

The matter of the lift-ship's destruction was fresh in Nordenfeld's
mind when Jensen had told his story. The two items fitted together with
an appalling completeness. They left little doubt or hope.

       *       *       *       *       *

Nordenfeld consulted the passenger records and presently was engaged in
conversation with the sober-faced, composed little girl on a sofa in
one of the cabin levels of the _Star Queen_.

"You're Kathy Brand, I believe," he said matter-of-factly. "I
understand you've been having a rather bad time of it."

She seemed to consider.

"It hasn't been too bad," she assured him. "At least I've been seeing
new things. I got dreadfully tired of seeing the same things all the
time."

"What things?" asked Nordenfeld. His expression was not stern now,
though his inner sensations were not pleasant. He needed to talk to
this child, and he had learned how to talk to children. The secret is
to talk exactly as to an adult, with respect and interest.

"There weren't any windows," she explained, "and my father couldn't
play with me, and all the toys and books were ruined by the water. It
was dreadfully tedious. There weren't any other children, you see. And
presently there weren't any grownups but my father."

Nordenfeld only looked more interested. He'd been almost sure ever
since knowing of the lift-ship's destruction and listening to Jensen's
account of the rumor the government of Altaira denied. He was horribly
sure now.

"How long were you in the place that hadn't any windows?"

"Oh, dreadfully long!" she said. "Since I was only six years old!
Almost half my life!" She smiled brightly at him. "I remember looking
out of windows and even playing out-of-doors, but my father and mother
said I had to live in this place. My father talked to me often and
often. He was very nice. But he had to wear that funny suit and keep
the glass over his face because he didn't live in the room. The glass
was because he went under the water, you know."

Nordenfeld asked carefully conversational-sounding questions. Kathy
Brand, now aged ten, had been taken by her father to live in a big room
without any windows. It hadn't any doors, either. There were plants in
it, and there were bluish lights to shine on the plants, and there was
a place in one corner where there was water. When her father came in to
talk to her, he came up out of the water wearing the funny suit with
glass over his face. He went out the same way. There was a place in
the wall where she could look out into another room, and at first her
mother used to come and smile at her through the glass, and she talked
into something she held in her hand, and her voice came inside. But
later she stopped coming.

       *       *       *       *       *

There was only one possible kind of place which would answer Kathy's
description. When she was six years old she had been put into some
university's aseptic-environment room. And she had stayed there. Such
rooms were designed for biological research. They were built and then
made sterile of all bacterial life and afterward entered through a tank
of antiseptic. Anyone who entered wore a suit which was made germ-free
by its passage through the antiseptic, and he did not breathe the air
of the aseptic room, but air which was supplied him through a hose, the
exhaled-air hose also passing under the antiseptic outside. No germ
or microbe or virus could possibly get into such a room without being
bathed in corrosive fluid which would kill it. So long as there was
someone alive outside to take care of her, a little girl could live
there and defy even chlorophage.

And Kathy Brand had done it. But, on the other hand, Kamerun was the
only planet where it would be necessary, and it was the only world
from which a father would land his small daughter on another planet's
spaceport. There was no doubt. Nordenfeld grimly imagined someone--he
would have had to be a microbiologist even to attempt it--fighting to
survive and defeat the chlorophage while he kept his little girl in an
aseptic-environment room.

She explained quite pleasantly as Nordenfeld asked more questions.
There had been other people besides her father, but for a long time
there had been only him. And Nordenfeld computed that somehow she'd
been kept alive on the dead planet Kamerun for four long years.

Recently, though--very recently--her father told her that they were
leaving. Wearing his funny, antiseptic-wetted suit, he'd enclosed her
in a plastic bag with a tank attached to it. Air flowed from the tank
into the bag and out through a hose that was all wetted inside. She
breathed quite comfortably.

It made sense. An air tank could be heated and its contents sterilized
to supply germ-free--or virus-free--air. And Kathy's father took an axe
and chopped away a wall of the room. He picked her up, still inside the
plastic bag, and carried her out. There was nobody about. There was no
grass. There were no trees. Nothing moved.

Here Kathy's account was vague, but Nordenfeld could guess at the
strangeness of a dead planet, to the child who barely remembered
anything but the walls of an aseptic-environment room.

Her father carried her to a little ship, said Kathy, and they talked
a lot after the ship took off. He told her that he was taking her to
a place where she could run about outdoors and play, but he had to go
somewhere else. He did mysterious things which to Nordenfeld meant a
most scrupulous decontamination of a small spaceship's interior and
its airlock. Its outer surface would reach a temperature at which no
organic material could remain uncooked.

And finally, said Kathy, her father had opened a door and told her to
step out and good-by, and she did, and the ship went away--her father
still wearing his funny suit--and people came and asked her questions
she did not understand.

       *       *       *       *       *

Kathy's narrative fitted perfectly into the rumor Jensen said
circulated among usually well-informed people on Altaira. They
believed, said Jensen, that a small spaceship had appeared in the sky
above Altaira's spaceport. It ignored all calls, landed swiftly, opened
an airlock and let someone out, and plunged for the sky again. And the
story said that radar telescopes immediately searched for and found
the ship in space. They trailed it, calling vainly for it to identify
itself, while it drove at top speed for Altaira's sun.

It reached the sun and dived in.

Nordenfeld reached the skipper on intercom vision-phone. Jensen had
been called there to repeat his tale to the skipper.

"I've talked to the child," said Nordenfeld grimly, "and I'm putting
her into isolation quarters in the hospital compartment. She's from
Kamerun. She was kept in an aseptic-environment room at some university
or other. She says her father looked after her. I get an impression of
a last-ditch fight by microbiologists against the chlorophage. They
lost it. Apparently her father landed her on Altaira and dived into
the sun. From her story, he took every possible precaution to keep her
from contagion or carrying contagion with her to Altaira. Maybe he
succeeded. There's no way to tell--yet."

The skipper listened in silence.

Jensen said thinly, "Then the story about the landing was true."

"Yes. The authorities isolated her, and then shipped her off on the
_Star Queen_. Your well-informed friends, Jensen, didn't know what
their government was going to do!" Nordenfeld paused, and said more
coldly still, "They didn't handle it right. They should have killed
her, painlessly but at once. Her body should have been immersed, with
everything that had touched it, in full-strength nitric acid. The
same acid should have saturated the place where the ship landed and
every place she walked. Every room she entered, and every hall she
passed through, should have been doused with nitric and then burned.
It would still not have been all one could wish. The air she breathed
couldn't be recaptured and heated white-hot. But the chances for
Altaira's population to go on living would be improved. Instead, they
isolated her and they shipped her off with us--and thought they were
accomplishing something by destroying the lift-ship that had her in an
airtight compartment until she walked into the _Star Queen's_ lock!"

The skipper said heavily, "Do you think she's brought chlorophage on
board?"

"I've no idea," said Nordenfeld. "If she did, it's too late to do
anything but drive the _Star Queen_ into the nearest sun.... No. Before
that, one should give warning that she was aground on Altaira. No ship
should land there. No ship should take off. Altaira should be blocked
off from the rest of the galaxy like Kamerun was. And to the same end
result."

Jensen said unsteadily; "There'll be trouble if this is known on the
ship. There'll be some unwilling to sacrifice themselves."

"Sacrifice?" said Nordenfeld. "They're dead! But before they lie down,
they can keep everybody they care about from dying too! Would you want
to land and have your wife and family die of it?"

The skipper said in the same heavy voice, "What are the probabilities?
You say there was an effort to keep her from contagion. What are the
odds?"

"Bad," said Nordenfeld. "The man tried, for the child's sake. But I
doubt he managed to make a completely aseptic transfer from the room
she lived in to the spaceport on Altaira. The authorities on Altaira
should have known it. They should have killed her and destroyed
everything she'd touched. And _still_ the odds would have been bad!"

Jensen said, "But you can't do that, Nordenfeld! Not now!"

"I shall take every measure that seems likely to be useful." Then
Nordenfeld snapped, "Damnation, man! Do you realize that this
chlorophage can wipe out the human race if it really gets loose? Do you
think I'll let sentiment keep me from doing what has to be done?"

He flicked off the vision-phone.

       *       *       *       *       *

The _Star Queen_ came out of overdrive. Her skipper arranged it to be
done at the time when the largest possible number of her passengers
and crew would be asleep. Those who were awake, of course, felt the
peculiar inaudible sensation which one subjectively translated into
sound. They felt the momentary giddiness which--having no natural
parallel--feels like the sensation of treading on a stair-step that
isn't there, combined with a twisting sensation so it is like a spiral
fall. The passengers who were awake were mostly in the bars, and the
bartenders explained that the ship had shifted overdrive generators and
there was nothing to it.

Those who were asleep started awake, but there was nothing in their
surroundings to cause alarm. Some blinked in the darkness of their
cabins and perhaps turned on the cabin lights, but everything seemed
normal. They turned off the lights again. Some babies cried and had to
be soothed. But there was nothing except wakening to alarm anybody.
Babies went back to sleep and mothers returned to their beds and--such
awakenings being customary--went back to sleep also.

It was natural enough. There were vague and commonplace noises,
together making an indefinite hum. Fans circulated the ship's purified
and reinvigorated air. Service motors turned in remote parts of the
hull. Cooks and bakers moved about in the kitchens. Nobody could tell
by any physical sensation that the _Star Queen_ was not in overdrive,
except in the control room.

There the stars could be seen. They were unthinkably remote. The ship
was light-years from any place where humans lived. She did not drive.
Her skipper had a family on Cassim. He would not land a plague ship
which might destroy them. The executive officer had a small son. If
his return meant that small son's death as well as his own, he would
not return. All through the ship, the officers who had to know the
situation recognized that if chlorophage had gotten into the _Star
Queen_, the ship must not land anywhere. Nobody could survive. Nobody
must attempt it.

So the huge liner hung in the emptiness between the stars, waiting
until it could be known definitely that chlorophage was aboard or that
with absolute certainty it was absent. The question was up to Doctor
Nordenfeld.

He had isolated himself with Kathy in the ship's hospital compartment.
Since the ship was built it had been used once by a grown man who
developed mumps, and once by an adolescent boy who developed a raging
fever which antibiotics stopped. Health measures for space travel were
strict. The hospital compartment had only been used those two times.

       *       *       *       *       *

On this voyage it had been used to contain an assortment of botanical
specimens from a planet seventy light-years beyond Regulus. They were
on their way to the botanical research laboratory on Cassim. As a
routine precaution they'd been placed in the hospital, which could
be fumigated when they were taken out. Now the doctor had piled them
in one side of the compartment, which he had divided in half with a
transparent plastic sheet. He stayed in that side. Kathy occupied the
other.

She had some flowering plants to look at and admire. They'd come from
the air room and she was delighted with their coloring and beauty.
But Doctor Nordenfeld had put them there as a continuing test for
chlorophage. If Kathy carried that murderous virus on her person, the
flowering plants would die of it--probably even before she did.

It was a scrupulously scientific test for the deadly stuff. Completely
sealed off except for a circulator to freshen the air she breathed,
Kathy was settled with toys and picture books. It was an improvised
but well-designed germproof room. The air for Kathy to breathe was
sterilized before it reached her. The air she had breathed was
sterilized as it left her plastic-sided residence. It should be the
perfection of protection for the ship--if it was not already too late.

The vision-phone buzzed. Doctor Nordenfeld stirred in his chair and
flipped the switch. The _Star Queen's_ skipper looked at him out of the
screen.

"I've cut the overdrive," said the skipper. "The passengers haven't
been told."

"Very sensible," said the doctor.

"When will we know?"

"That we can go on living? When the other possibility is exhausted."

"Then, how will we know?" asked skipper stonily.

Doctor Nordenfeld ticked off the possibilities. He bent down a finger.
"One, her father took great pains. Maybe he did manage an aseptic
transfer from a germ-free room to Altaira. Kathy may not have been
exposed to the chlorophage. If she hasn't, no bleached spots will show
up on the air-room foliage or among the flowering plants in the room
with her. Nobody in the crew or among the passengers will die."

He bent down a second finger. "It is probably more likely that white
spots will appear on the plants in the air room _and_ here, and people
will start to die. That will mean Kathy brought contagion here the
instant she arrived, and almost certainly that Altaira will become like
Kamerun--uninhabited. In such a case we are finished."

       *       *       *       *       *

He bent down a third finger. "Not so likely, but preferable, white
spots may appear on the foliage inside the plastic with Kathy, but not
in the ship's air room. In that case she was exposed, but the virus was
incubating when she came on board, and only developed and spread after
she was isolated. Possibly, in such a case, we can save the passengers
and crew, but the ship will probably have to be melted down in space.
It would be tricky, but it might be done."

The skipper hesitated. "If that last happened, she--"

"I will take whatever measures are necessary," said Doctor Nordenfeld.
"To save your conscience, we won't discuss them. They should have been
taken on Altaira."

He reached over and flipped off the phone. Then he looked up and into
the other part of the ship's hospital space. Kathy came out from behind
a screen, where she'd made ready for bed. She was beaming. She had a
large picture book under one arm and a doll under the other.

"It's all right for me to have these with me, isn't it, Doctor
Nordenfeld?" she asked hopefully. "I didn't have any picture books but
one, and it got worn out. And my doll--it was dreadful how shabby she
was!"

The doctor frowned. She smiled at him. He said, "After all, picture
books are made to be looked at and dolls to be played with."

She skipped to the tiny hospital bed on the far side of the presumably
virusproof partition. She climbed into it and zestfully arranged the
doll to share it. She placed the book within easy reach.

She said, "I think my father would say you were very nice, Doctor
Nordenfeld, to look after me so well."

"No-o-o-o," said the doctor in a detached voice. "I'm just doing what
anybody ought to do."

She snuggled down under the covers. He looked at his watch and
shrugged. It was very easy to confuse official night with official day,
in space. Everybody else was asleep. He'd been putting Kathy through
tests which began with measurements of pulse and respiration and
temperature and went on from there. Kathy managed them herself, under
his direction.

He settled down with one of the medical books he'd brought into
the isolation section with him. Its title was _Decontamination of
Infectious Material from Different Planets_. He read it grimly.

       *       *       *       *       *

The time came when the _Star Queen_ should have come out of overdrive
with the sun Circe blazing fiercely nearby, and a green planet with
ice caps to be approached on interplanetary drive. There should have
been droning, comforting drive noises to assure the passengers--who
naturally could not see beyond the ship's steel walls--that they were
within a mere few million miles of a world where sunshine was normal,
and skies were higher than ship's ceilings, and there were fascinating
things to see and do.

Some of the passengers packed their luggage and put it outside their
cabins to be picked up for landing. But no stewards came for it.
Presently there was an explanation. The ship had run under maximum
speed and the planetfall would be delayed.

The passengers were disappointed but not concerned. The luggage
vanished into cabins again.

The _Star Queen_ floated in space among a thousand thousand million
stars. Her astrogators had computed a course to the nearest star into
which to drive the _Star Queen_, but it would not be used unless there
was mutiny among the crew. It would be better to go in remote orbit
around Circe III and give the news of chlorophage on Altaira, if Doctor
Nordenfeld reported it on the ship.

Time passed. One day. Two. Three. Then Jensen called the hospital
compartment on vision-phone. His expression was dazed. Nordenfeld saw
the interior of the control room behind Jensen. He said, "You're a
passenger, Jensen. How is it you're in the control room?"

Jensen moistened his lips. "The skipper thought I'd better not
associate with the other passengers. I've stayed with the officers the
past few days. We--the ones who know what's in prospect--we're keeping
separate from the others so--nobody will let anything out by accident."

"Very wise. When the skipper comes back on duty, ask him to call me.
I've something interesting to tell him."

"He's--checking something now," said Jensen. His voice was thin and
reedy. "The--air officer reports there are white patches on the plants
in the air room. They're growing. Fast. He told me to tell you.
He's--gone to make sure."

"No need," said Nordenfeld bitterly.

He swung the vision-screen. It faced that part of the hospital space
beyond the plastic sheeting. There were potted flowering plants there.
They had pleased Kathy. They shared her air. And there were white
patches on their leaves.

"I thought," said Nordenfeld with an odd mirthless levity, "that the
skipper'd be interested. It is of no importance whatever now, but
I accomplished something remarkable. Kathy's father didn't manage
an aseptic transfer. She brought the chlorophage with her. But I
confined it. The plants on the far side of that plastic sheet show the
chlorophage patches plainly. I expect Kathy to show signs of anemia
shortly. I'd decided that drastic measures would have to be taken,
and it looked like they might work, because I've confined the virus.
It's there where Kathy is, but it isn't where I am. All the botanical
specimens on my side of the sheet are untouched. The phage hasn't hit
them. It is remarkable. But it doesn't matter a damn if the air room's
infected. And I was so proud!"

Jensen did not respond.

       *       *       *       *       *

Nordenfeld said ironically, "Look what I accomplished! I protected
the air plants on my side See? They're beautifully green! No sign of
infection! It means that a man can work with chlorophage! A laboratory
ship could land on Kamerun and keep itself the equivalent of an
aseptic-environment room while the damned chlorophage was investigated
and ultimately whipped! And it doesn't matter!"

Jensen said numbly, "We can't ever make port. We ought--we ought to--"

"We'll take the necessary measures," Nordenfeld told him. "Very quietly
and very efficiently, with neither the crew nor the passengers knowing
that Altaira sent the chlorophage on board the _Star Queen_ in the hope
of banishing it from there. The passengers won't know that their own
officials shipped it off with them as they tried to run away.... And
I was so proud that I'd improvised an aseptic room to keep Kathy in! I
sterilized the air that went in to her, and I sterilized--"

Then he stopped. He stopped quite short. He stared at the air unit, set
up and with two pipes passing through the plastic partition which cut
the hospital space in two. He turned utterly white. He went roughly to
the air machine. He jerked back its cover. He put his hand inside.

Minutes later he faced back to the vision-screen from which Jensen
looked apathetically at him.

"Tell the skipper to call me," he said in a savage tone. "Tell him to
call me instantly he comes back! Before he issues any orders at all!"

He bent over the sterilizing equipment and very carefully began to
disassemble it. He had it completely apart when Kathy waked. She peered
at him through the plastic separation sheet.

"Good morning, Doctor Nordenfeld," she said cheerfully.

The doctor grunted. Kathy smiled at him. She had gotten on very good
terms with the doctor, since she'd been kept in the ship's hospital.
She did not feel that she was isolated. In having the doctor where she
could talk to him at any time, she had much more company than ever
before. She had read her entire picture book to him and discussed her
doll at length. She took it for granted that when he did not answer or
frowned that he was simply busy. But he was company because she could
see him.

Doctor Nordenfeld put the air apparatus together with an extremely
peculiar expression on his face. It had been built for Kathy's special
isolation by a ship's mechanic. It should sterilize the used air going
into Kathy's part of the compartment, and it should sterilize the
used air pushed out by the supplied fresh air. The hospital itself
was an independent sealed unit, with its own chemical air freshener,
and it had been divided into two. The air freshener was where Doctor
Nordenfeld could attend to it, and the sterilizer pump simply shared
the freshening with Kathy. But--

But the pipe that pumped air to Kathy was brown and discolored from
having been used for sterilizing, and the pipe that brought air back
was not. It was cold. It had never been heated.

So Doctor Nordenfeld had been exposed to any contagion Kathy could
spread. He hadn't been protected at all. Yet the potted plants on
Kathy's side of the barrier were marked with great white splotches
which grew almost as one looked, while the botanical specimens in the
doctor's part of the hospital--as much infected as Kathy's could have
been, by failure of the ship's mechanic to build the sterilizer to work
two ways: the stacked plants, the alien plants, the strange plants from
seventy light-years beyond Regulus--they were vividly green. There
was no trace of chlorophage on them. Yet they had been as thoroughly
exposed as Doctor Nordenfeld himself!

The doctor's hands shook. His eyes burned. He took out a surgeon's
scalpel and ripped the plastic partition from floor to ceiling. Kathy
watched interestedly.

"Why did you do that, Doctor Nordenfeld?" she asked.

He said in an emotionless, unnatural voice, "I'm going to do something
that it was very stupid of me not to do before. It should have been
done when you were six years old, Kathy. It should have been done on
Kamerun, and after that on Altaira. Now we're going to do it here. You
can help me."

       *       *       *       *       *

The _Star Queen_ had floated out of overdrive long enough to throw all
distance computations off. But she swung about, and swam back, and
presently she was not too far from the world where she was now many
days overdue. Lift-ships started up from the planet's surface. But the
_Star Queen_ ordered them back.

"Get your spaceport health officer on the vision-phone," ordered the
_Star Queen's_ skipper. "We've had chlorophage on board."

There was panic. Even at a distance of a hundred thousand miles,
chlorophage could strike stark terror into anybody. But presently the
image of the spaceport health officer appeared on the _Star Queen's_
screen.

"We're not landing," said Doctor Nordenfeld. "There's almost certainly
an outbreak of chlorophage on Altaira, and we're going back to do
something about it. It got on our ship with passengers from there.
We've whipped it, but we may need some help."

The image of the health officer aground was a mask of horror for
seconds after Nordenfeld's last statement. Then his expression became
incredulous, though still horrified.

"We came on to here," said Doctor Nordenfeld, "to get you to send
word by the first other ship to the Patrol that a quarantine has
to be set up on Altaira, and we need to be inspected for recovery
from chlorophage infection. And we need to pass on, officially, the
discovery that whipped the contagion on this ship. We were carrying
botanical specimens to Cassim and we discovered that they were immune
to chlorophage. That's absurd, of course. Their green coloring is the
same substance as in plants under Sol-type suns anywhere. They couldn't
be immune to chlorophage. So there had to be something else."

"Was--was there?" asked the health officer.

"There was. Those specimens came from somewhere beyond Regulus. They
carried, as normal symbiotes on their foliage, microörganisms unknown
both on Kamerun and Altaira. The alien bugs are almost the size of
virus particles, feed on virus particles, and are carried by contact,
air, and so on, as readily as virus particles themselves. We discovered
that those microörganisms devoured chlorophage. We washed them off the
leaves of the plants, sprayed them in our air-room jungle, and they
multiplied faster than the chlorophage. Our whole air supply is now
loaded with an airborne antichlorophage organism which has made our
crew and passengers immune. We're heading back to Altaira to turn loose
our merry little bugs on that planet. It appears that they grow on
certain vegetation, but they'll live anywhere there's phage to eat.
We're keeping some chlorophage cultures alive so our microörganisms
don't die out for lack of food!"

The medical officer on the ground gasped. "Keeping phage _alive_?"

       *       *       *       *       *

"I hope you've recorded this," said Nordenfeld. "It's rather important.
This trick should have been tried on Kamerun and Altaira and everywhere
else new diseases have turned up. When there's a bug on one planet
that's deadly to us, there's bound to be a bug on some other planet
that's deadly to it! The same goes for any pests or vermin--the
principle of natural enemies. All we have to do is find the enemies!"

There was more communication between the _Star Queen_ and the spaceport
on Circe III, which the _Star Queen_ would not make other contact with
on this trip, and presently the big liner headed back to Altaira. It
was necessary for official as well as humanitarian reasons. There would
need to be a health examination of the _Star Queen_ to certify that it
was safe for passengers to breathe her air and eat in her restaurants
and swim in her swimming pools and occupy the six levels of passenger
cabins she contained. This would have to be done by a Patrol ship,
which would turn up at Altaira.

The _Star Queen's_ skipper would be praised by his owners for not
having driven the liner into a star, and the purser would be forgiven
for the confusion in his records due to off-schedule operations of
the big ship, and Jensen would find in the ending of all terror of
chlorophage an excellent reason to look for appreciation in the value
of the investments he was checking up. And Doctor Nordenfeld....

He talked very gravely to Kathy. "I'm afraid," he told her, "that your
father isn't coming back. What would you like to do?"

She smiled at him hopefully. "Could I be your little girl?" she asked.
Doctor Nordenfeld grunted. "Hm ... I'll think about it."

But he smiled at her. She grinned at him. And it was settled.