IV

"Statistically, it must be recognized that no human action is

without consequences to the man who acts. Again statistically, it

must be recognized that the consequences of an action tend with

strong probability to follow the general pattern of the action. A

violent action, for example, has a strong probability of violent

consequences, and since some at least of the consequences of an

act must affect the person acting, a man who acts violently exposes

himself to the probability that chance consequences which affect

him, if unfavorable, will be violently so."

_Probability and Human Conduct_

Fitzgerald

Murgatroyd had been inoculated with a blood-sample from the girl Helen

some three hours or less before sunset. But it was one of the more

valuable genetic qualities of the _tormal_ race that they reacted to

bacterial infection as a human being reacts to medication. Medicine on

the skin of a human being rarely has any systemic effect. Medication on

mucus membrane penetrates better. Ingested medication--medicine that

is swallowed--has greater effectiveness still. But substances injected

into tissues or the blood-stream have most effect of all. A centigram

of almost any drug administered by injection will have an effect

close to that of a gram taken orally. It acts at once and there is no

modification by gastric juices.

Murgatroyd had had half a cubic centimeter of the girl's blood injected

into the spot on his flank where he could feel no pain. It contained

the unknown cause of the plague on Maris III. Its effect as injected

was incomparably greater than the same infectious material smeared

on his skin or swallowed. In either such case, of course, it would

have had no effect at all, because _tormals_ were to all intents and

purposes immune to ordinary contagions. Just as they had a built-in

unit in their digestive tract to cause the instant rejection of

unwholesome food, their body-cells had a built-in ability to produce

antibodies immediately the toxin of a pathogenic organism came into

contact with them. So _tormals_ were effectively safe against any

disease transmitted by ordinary methods of infection. Yet if a culture

of pathogenic bacteria--say--were injected into their blood stream,

their whole body set to work to turn out antibodies because all

their body was attacked. And all at once. There was practically no

incubation-period.

Murgatroyd, who had been given the plague in mid-afternoon, was

reacting violently to its toxins by sunset. But two hours after

darkness fell he arose and said shrilly, "_Chee-chee-chee!_" He'd been

sunk in heavy slumber. When he woke, there was a small fire in the

glade, about which the exhausted, emaciated fugitives consulted with

Calhoun. Calhoun was saying bitterly:

"Those characters in the city are immune! They have to be! And they

know they're immune, or they wouldn't risk contagion by murdering you

or handling the bodies of plague-victims to burn them! So they have to

know all about the plague--and they knew it before they arrived! They

came because they knew! That's why I shot that man with the crossbow,

instead of taking a blaster to him. I meant to wound him so I could

make him answer questions, but it's not an accurate weapon and I killed

him instead. I got very little from the stuff in his pockets. The

only significant thing was a ground-car key, and even that means only

there's a car waiting somewhere for him."

The gaunt young man said drearily:

"He didn't come from Dettra, our home planet. Fashions are different on

different worlds. His foot-wear was like a style we had on Dettra four

years back, and his body-clothing has fasteners we don't use."

Murgatroyd saw Calhoun and rushed to him, embracing his legs with

enthusiasm and chattering shrilly of his relief at finding the man he

knew. The skeletonlike plague-victims stared at him.

"This," said Calhoun with infinite relief, "is Murgatroyd. He's had the

plague and is over it. So now we'll get you people cured. I wish I had

better light!"

He counted Murgatroyd's breathing and listened to his heart. Murgatroyd

was in that state of boisterous good health which is normal in any

lower animal, but amounts to genius in a _tormal_. Calhoun regarded him

with satisfaction.

"All right!" he said. "Come along!"

* * * * *

He plucked a brand of burning resinous stuff from the campfire. He

handed it to the gaunt young man and led the way. Murgatroyd ambled

complacently after him. Calhoun stopped under one of the unoccupied

shelters and got out his lab kit. He bent over Murgatroyd. What he did,

did not hurt. When he stood up, he squinted at the red fluid in the

instrument he'd used.

"About fifteen CCs," he observed. "This is strictly emergency stuff I'm

doing now. But I'd say that there's an emergency."

The gaunt young man said:

"I'd say you've doomed yourself. The incubation-period seems to be

about six days. It took that long to develop among the doctors we had

in the office staff."

Calhoun opened a compartment of the kit, whose minuscule test tubes

and pipettes gleamed in the torchlight. He absorbedly transferred the

reddish fluid to a miniature filter-barrel, piercing a self-healing

plastic cover to do so. He said:

"You're pre-med? The way you talk--"

"I was an interne," said Kim. "Now I'm pre-corpse."

"I doubt that last," said Calhoun. "But I wish I had some distilled

water--This is anticoagulant." He added the trace of a drop to the

sealed, ruddy fluid. He shook the whole filter to agitate it. The

instrument was hardly larger than his thumb. "Now a clumper--" He added

a minute quantity of a second substance from an almost microscopic

ampule. He shook the filter again. "You can guess what I'm doing.

With a decent lab I'd get the structure and formula of the antibody

Murgatroyd has so obligingly turned out for us. We'd set to work to

synthesize it. In twenty hours, lab time, we ought to have it coming

out of the reaction-flasks in quantity. But there is no lab."

"There's one in the city," said the gaunt young man hopelessly. "It was

for the colonists who were to come. And we were staffed to give them

proper medical care. When the plague came, our doctors did everything

imaginable. They not only tried the usual culture tricks, but they

cultured samples of every separate tissue in the fatal cases. They

never found a single organism--even in the electron microscopes--that

would produce the plague." He said with a sort of weary pride, "Those

who'd been exposed worked until they had it, then others took over.

Every man worked as long as he could make his brain work, though."

Calhoun squinted through the glass tube of the filter at the

sputtering torch.

"Almost clumped," he observed. Then he said, "Did you ever hear of a

man named Pasteur? One of his first discoveries was that one could get

an effectively pure culture of a pathogenic organism by giving the

disease to an experimental animal. Better ways were found later, but

one still expects a pure culture in a patient who has a disease really

badly. What did the lab turn up?"

Kim shook his head.

"Nothing. The bacteriological survey of the planet had been thorough.

Oral and intestinal flora were normal. Naturally, the local bacteria

couldn't compete with the strains we humans have learned to live with.

They couldn't symbiotize. So there wasn't anything unknown. There

wasn't any cause of the plague."

Calhoun began to work the filter plunger, by the wavering light of

the torch. The piston was itself the filter, and on one side a clear,

mobile liquid began very slowly to appear.

"Mutated standard bug? Still, if your doctors did cultures and couldn't

reproduce the disease--"

"They could pass it," said Kim bitterly, "but they could never find

what carried it! No pure culture would!"

* * * * *

Calhoun watched the clear fluid develop on the delivery side of the

filtering piston. The job got done. There was better than twelve cubic

centimeters of clear serum on the delivery side, and an almost solid

block of clumped blood cells on the other. He drew off the transparent

fluid with a fine precision.

"We're doing biochemistry under far from aseptic conditions," he said

wryly, "but the work has to be done and we have to take the risk.

Anyhow, I'm getting a feeling that this isn't any ordinary plague. A

normal pathogenic organism should have been turned up by your doctors."

"It wasn't," said Kim.

"So," said Calhoun, "maybe it isn't one isolatable organism. Maybe

the disease-producing mechanism simply isn't there when you make pure

cultures of the separate strains of virus and microbe. Murgatroyd was

a pretty sick animal. I've only known of one previous case in which

a _tormal_ reacted as violently as Murgatroyd did. That one had us

sweating."

"If I were going to live," said Kim grimly, "I might ask what it was."

"Since you're going to," Calhoun told him, "I'll tell you though you

don't. It was a pair of organisms. Their toxins acted synergically

together. Separately they were innocuous. Together they were

practically explosive. That one was the devil to track down!"

He went back across the glade. Murgatroyd came skipping after him,

scratching at the anaesthetic patch on his hide, which he sometimes

seemed to notice not because it felt oddly, but because it did not feel

at all.

"You," said Calhoun briefly to Helen Jons, "you go first. This is an

antibody serum. You may itch afterward, but I doubt it. Your arm,

please."

She bared her rather pitifully thin arm. He gave her practically a

CC of fluid which--plus blood-corpuscles and some forty-odd other

essential substances--had been circulating in Murgatroyd's blood stream

not long since. The blood-corpuscles had been clumped and removed by

one compound plus the filter, and the anticoagulant had neatly modified

most of the others. In a matter of minutes, the lab kit had prepared as

usable a serum as any animal-using technique would produce. Logically,

the antibodies it contained should be isolated and their chemical

structure determined. They should be synthesized, and the synthetic

antibody-complex administered to plague-victims. But Calhoun faced a

small group of people doomed to die. He could only use his field kit

to produce a small-scale miracle for them. He could not do a mass

production job.

"Next!" said Calhoun. "Tell them what it's all about, Kim!"

The gaunt young man bared his own arm.

"If what he says is so, this will cure us. If it isn't so, nothing can

do us any harm!"

And Calhoun briskly gave them, one after another, the shots of what

ought to be a curative serum for an unidentified disease which he

suspected was not caused by any single germ, but by a partnership.

Synergy is an acting-together. Charcoal will burn quietly. Liquid

air will not burn at all. But the two together constitute a violent

explosive. This is analogous to synergy. The ancient simple drug sulfa

is not intoxicating. A glass of wine is not intoxicating. But the two

together have the kick of dynamite. Synergy, in medicine, is a process

in which when one substance with one effect is given in combination

with another substance with another effect, the two together have the

consequences of a third substance intensified to fourth or fifth or

tenth power.

* * * * *

"I think," said Calhoun when he'd finished, "that by morning you'll

feel better--perhaps cured of the plague and only weak from failure

to force yourselves to take nourishment. If it turns out that way,

I advise you all to get as far away from the city as possible for a

considerable while. I think this planet is going to be repopulated. I

suspect that shiploads of colonists are on the way here now--but not

from Dettra, which built the city. And I definitely guess that, sick

or well, you're going to be in trouble if or when you contact the new

colonists."

They looked tiredly at him. They were a singular lot of people. Each

one seemed half-starved, yet their eyes had not the brightness of

suffering. They looked weary beyond belief, and yet there was not

self-neglect. They were of that singular human type which maintains

human civilization against the inertia of the race--because it drives

itself to get needed things done. It is not glamorous, this dogged part

of mankind which keeps things going. It is sometimes absurd. For dying

folk to wash themselves, when even such exertion calls for enormous

resolution, is not exactly rational. To help each other try to die with

dignity was much more a matter of self-respect than of intellectual

decision. But as a Med Ship man, Calhoun viewed them with some warmth.

They were the type that has to be called on when an emergency occurs

and the wealth-gathering type tends to flee and the low-time-sense part

of a population inclines to riot or loot or worse.

Now they waited listlessly for their own deaths.

"There's no exact precedent for what's happened here," explained

Calhoun. "A thousand years or so ago there was a king of France--a

country back on old Earth--who tried to wipe out a disease called

leprosy by executing all the people who had it. Lepers were a nuisance.

They couldn't work. They had to be fed by charity. They died in

inconvenient places and only other lepers dared handle their bodies.

They tended to throw normal human life out of kilter. That wasn't the

case here. The man I killed wanted you dead for another reason. He

wanted you dead right away."

The gaunt Kim Walpole said tiredly:

"He wanted to dispose of our bodies in a sanitary fashion."

"Nonsense!" snapped Calhoun. "The city's infected. You lived, ate,

breathed, walked in it. Nobody can dare use that city unless they know

how the contagion's transmitted, and how to counteract it. Your own

colonists turned back. These men wouldn't have landed if they hadn't

known they were safe!"

There was silence.

"If the plague is an intended crime," added Calhoun, "you are the

witnesses to it. You've got to be gotten rid of before colonists from

somewhere other than Dettra arrive here."

The dark-bearded man growled:

"Monstrous! Monstrous!"

"Agreed," said Calhoun. "But there's no interstellar government, now,

any more than there was a planetary government in the old days back on

Earth. So if somebody pirates a colony ready to be occupied, there's

no authority able to throw them out. The only recourse would be war.

And nobody is going to start an interplanetary war! Not with the bombs

that can be landed! If the invaders can land a population here, they

can keep it here. It's piracy, with nobody able to do anything to the

pirates." He paused, and said with irony: "Of course they could be

persuaded that they were wrong."

But that was not even worth thinking about. In the computation of

probabilities in human conduct, self-interest is a high-value factor.

Children and barbarians have clear ideas of justice due to them, but

no idea at all of justice due from them. And though human colonies

spread toward the galaxy's rim, there was still a large part of every

population which was civilized only in that it could use tools. Most

people still remained comfortably barbaric or childish in their

emotional lives. It was a fact that had to be considered in Calhoun's

profession. It bore remarkably on matters of health.

"So you'll have to hide. I think permanently," Calhoun told them. "But

in the morning, after I've checked on you people again, I think I'll

go into the city and see what I can do about it. Try to rest now. You

should all feel much better in the morning."

Kim Walpole said abruptly:

"You've been exposed to the plague. Have you protected yourself?"

"Not yet," acknowledged Calhoun. "Give me a quarter of a CC."

He handed the injector to the gaunt young man. He noted the precision

with which Kim handled it. Then he helped get the survivors of the

original group--there were six of them--to the leafy beds under the

shelters. They were very quiet--even more quiet than their illness

demanded. They were very polite. The old man and woman who had

struggled back to the glade together made an especial attempt to bid

Calhoun good night with the courtesy appropriate to city folk of

tradition.

Calhoun settled down to keep watch through the night. Murgatroyd

snuggled confidingly close to him. There was silence.

* * * * *

But not complete silence. The night of Maris III was filled with tiny

noises, and some not so tiny. There were little squeaks which seemed

to come from all directions, including overhead. There were chirpings

which were definitely at ground-level. There was a sound like effortful

grunting somewhere in the direction of the rampart of hills. In the

lowlands there was a rumbling which moved very slowly from one place to

another. By its rate of motion, Calhoun guessed that a pack or herd of

small animals was making a night-journey and uttering deep-bass noises

as it traveled.

He debated certain grim possibilities. The man he'd killed had had

a ground-car key in his pocket. He'd probably come out in a powered

vehicle. He might have had a companion, and the method of hunting down

fugitives--successful, in his case--was probably well established. That

companion might come looking for him, so watchfulness was necessary.

Meanwhile--the plague. The idea of synergy was still most plausible.

Suppose the toxins--the poisonous metabolic products--of two separate

kinds of bacteria combined to lessen the ability of the blood to

carry oxygen and scavenge away carbon dioxide? It would be extremely

difficult to identify the pair, and the symptoms would be accounted

for. No pure culture of any organism to be found would give the

plague. Each, by itself, would be harmless. Only a combination of two

would be injurious. And if so much was assumed--why--if the blood

lost its capacity to carry oxygen, mental listlessness would be the

first symptom of all. The brain requires a high oxygen-level in its

blood-supply if it is to work properly. Let a man's brain be gradually,

slowly, starved of oxygen and all the noted effects would follow.

His other organs would slow down, but at a lesser rate. He would not

remember to eat. His blood would still digest food and burn away its

own fat--though more and more sluggishly--while his brain worked only

foggily. He would become only semiconscious, and then there would come

a time of coma when unconsciousness claimed him and his body lived on

only as an idling machine--until it ran out of fuel and died.

Calhoun tried urgently to figure out a synergic combination which

might make a man's blood cease to do its work. Perhaps only minute

quantities of the dual poison might be needed--like an antivitamin or

an antienzyme, or--

The invaders of the city were immune. Quite possibly the same

antibodies Murgatroyd had produced were responsible for their safety.

Somewhere, somebody had very horribly used the science of medicine to

commit a monstrous crime. But the science of medicine--

A savage idea came to Calhoun. Its practicality might depend on the

number of men in the city. But his eyes burned.

He heard a movement across the glade. He reached for his blaster. Then

he saw where the motion was. It was Kim Walpole, intolerably weary,

trudging with infinite effort to where Helen Jons lay. Calhoun heard

him ask heavily:

"You're all right?"

"Yes, Kim," said the girl softly. "I couldn't sleep. I'm ... wondering

if we can hope."

Kim did not answer.

"If we live--" said the girl yearningly, and stopped.

Calhoun felt that he ought to put his fingers in his ears. The

conversation was strictly private. But he needed to be on guard. So he

coughed, to give notice that he heard. Kim called to him across the

starlit glade.

"Calhoun."

"Yes," said Calhoun. "If you two talk, I suggest that you do it in

whispers. I want to listen, in case the man I killed had friends who'll

come looking for him. Did you get his blaster, by the way?"

"Yes," said Kim from the darkness across the way.

"Good!" said Calhoun. "Keep it. And against all medical ethics, I

advise you to use it freely if you find suitable targets. But now,

just talk quietly if you can."

He settled back. Murgatroyd stirred and cuddled closer against him

without wakening. There was the faintest possible murmuring of

voices where Kim Walpole and the girl Helen talked wistfully of the

possibility of hope.

Calhoun felt very lonely, despite the violent activities he foresaw for

the morrow. He almost envied Kim Walpole. But he could not have traded

places with him. It wouldn't have been a fair trade. Calhoun was quite

confident that--via Murgatroyd--the folk in the glade had a very fair

chance of living for some time yet.

His own chances, considering what he had to do, were more nearly zero.

Just about zero, when considered dispassionately.

V

"Very much of physical science is merely the comprehension of

long-observed facts. In human conduct, there is a long tradition of

observation, but a very brief record of comprehension. For example,

human life in contact with other human lives follows the rules of

other ecological systems. All too often, however, a man may imagine

that an ecological system is composed only of things, whereas such

a system operates through the actions of things. It is not possible

for any part of an ecological complex to act upon the other parts

without being acted upon, in its turn. So that it is singularly

stupid--and singularly common--for an individual to consider human

society as passive and unreactive, so that he may do what he pleases

without a reaction as energetic as his action, and as well-directed.

Moreover, probability--."

_Probability and Human Conduct_

Fitzgerald

An hour after sunrise Calhoun's shoulder-pack was empty of food. The

refugees arose, and they were weak and ravenous. Their respiration

had slowed to normal. Their pulses no longer pounded. Their eyes were

no longer dull, but very bright. But they were in advanced states

of malnutrition, and only now were aware of it. Their brains were

again receiving adequate oxygen and their metabolism was at a normal

level--and they knew that they were starving.

Calhoun served as cook. He trudged to the spring that Helen described

and brought back water. While they sucked on sweet tablets from his

rations and watched with hungry eyes, he made soup from the dehydrated

rations he'd carried for Murgatroyd and himself. He gave it to them as

the first thing their stomachs were likely to digest.

He watched as they fed themselves. The elderly man and woman consumed

it delicately, looking at each other. The man with the broad dark beard

ate with enormous self-restraint. Helen fed the weakest oldest man,

between spoonfuls for herself, and Kim Walpole ate slowly, brooding.

Calhoun drew him aside.

"During the night," he said, "I got another lot of serum ready. I'm

leaving it with you, with an injector. You'll find other refugees. I

gave you massive doses. You'd better be stingy. Try half-CC shots."

"What about you?" demanded Kim.

Calhoun shrugged.

"You'd be surprised how much authority I have--when I can make it

stick," he said dryly. "As a Med Ship man I've authority to take

complete charge of any health emergency. You people have a hitherto

unknown plague here. That's one emergency. The present inhabitants of

the city haven't got it. That's another. So since I have authority and

reason to exercise it if I can, I'm going to the city to take a little

action."

"You'll be killed," said Kim.

"Possibly," admitted Calhoun. "But the number of chance happenings

that could favor me is very much greater than the number of breaks

that could favor the invaders. And there's the matter of colonists.

Prospective colonists. You're being hunted so hard that they must be

about due. They've probably been immunized against this plague, but

technically I shouldn't let them land on a plague-stricken planet."

Kim Walpole stared.

"You mean you'll try to stop them?"

"I shall try," said Calhoun, "to implement the authority vested in me

by the Med Service for such cases as this. The rules about quarantine

are rather strict."

"You'll be killed," said Kim, again.

Calhoun ignored the repeated prediction.

"That hunter found you," he observed, "because he knew that you'd have

to drink. So he found a brook and followed it up, looking for signs of

humans drinking from it. He found footprints about the spring. I found

his footprints there, too. That's the trick you'll use to find other

fugitives. But pass on the word not to leave tracks hereafter. For

other advice, I advise you to get all the weapons you can. Modern ones,

of course. You've got the blaster from the man I killed."

"I think," said Kim between his teeth, "that I'll get some more. If

hunters from the city do track us to our drinking places, I'll know how

to get more weapons!"

"Yes," agreed Calhoun, and added, "Murgatroyd made the antibodies

that cured you. As a general rule, you can expect antibody production

in your own bodies once an infection begins to be licked. In case of

extreme emergency, each of you can probably supply antibodies for a

fair number of other plague-victims. You might try serum from blisters

you produce on your skin. Quite often antibodies turn up there. I don't

guarantee it, but sometimes it works."

He paused. Kim Walpole said harshly:

"But you! Isn't there anything we can do for you?"

"I was going to ask you something," said Calhoun. He produced the

telephoto films of the city as photographed from space. "There's a

laboratory in the city--a biochemistry lab. Show me where to look for

it."

Walpole gave explicit directions, pointing out the spot on the photo.

Calhoun nodded. Then Kim said fiercely:

"But tell us something we can do! We'll be strong, presently! We'll

have weapons! We'll track down-stream to where hunters leave their

ground-cars and be equipped with them! We can help you!"

Calhoun nodded approvingly.

"Right. If you see the smoke of a good-sized fire in the city, and if

you've got a fair number of fairly strong men with you, and if you've

got ground-cars, you might investigate. But be cagey about it! Very

cagey!"

"If you signal we'll come," said Kim Walpole grimly, "no matter how few

we are!"

"Fine!" said Calhoun. He had no intention of calling on these weakened,

starveling people for help.

* * * * *

He swung his depleted pack on his back again and slipped away from the

glade. He made his way to the spring, which flowed clear and cool from

unseen depths. He headed down the little brook which flowed away from

it. Murgatroyd raced along its banks. He hated to get his paws wet.

Presently, where the underbrush grew thickly close to the water's edge,

Murgatroyd wailed. "_Chee! Chee!_" And Calhoun plucked him from the

ground and set him on his shoulder. Murgatroyd clung blissfully there

as Calhoun followed down the stream bed. He adored being carried.

Two miles down, there was another cultivated field. This one was set

out to a gigantized root-crop, and Calhoun walked past shoulder-high

bushes with four-inch blue-and-white flowers. He recognized the

plants as of the family _solanaceae_--belladona was still used in

medicine--but he couldn't identify it until he dug up a root and found

a potato. But the six-pound specimen he uncovered was still too young

and green to be eaten. Murgatroyd refused to touch it.

Calhoun was ruefully considering the limitations of specialized

training when he came to the end of the cultivated field. There was

a highway. It was new, of course. City, fields, highways and all

the appurtenances of civilized life had been built on this planet

before the arrival of the colonists who were to inhabit it. It was

extraordinary to see such preparations for a population not yet on

hand. But Calhoun was much more interested in the ground-car he found

waiting on the highway, hard by a tiny bridge under which the brook he

followed flowed.

The key he'd taken from the hunter fitted. He got in and put Murgatroyd

on the seat beside him.

"These invaders, Murgatroyd," he observed, "must be in a bad way. A

newly-built city which was never occupied will be like an empty house.

There's no amusement or loot to be found in prowling it. They were

sent to take over the planet, and they've done it. But they've nothing

to do now, except hunt refugees--until their colonists arrive. I

suspect they're bored. We'll try to fix that!"

He set the ground-car in motion. Toward the city.

It was a full twenty miles, but he did not encounter a single other

vehicle. Presently the city lay spread out before him. He stopped and

surveyed the vast pile. It was a very beautiful city. Fifty generations

of architects on many worlds had played with stone and steel, groping

for the perfect combination of materials with design. This city was a

product of their tradition. There were towers which glittered whitely,

and low buildings which seemed to nestle on the vegetation-covered

ground. There were soaring bridges, and gracefully curving highways,

and park areas laid out and ready. There was no monotony anywhere.

The only exception to gracefulness was the sturdy landing grid itself,

half a mile high and a mile across, which was a lace-work of massive

steel girders with spider-thin lines of copper woven about in the

complex curves the creation of its force-field required. Inside it,

Calhoun could see the ship of the invaders. It had been brought down

inside the circular structure and was dwarfed by it. It gleamed there.

"And we," said Calhoun, "are going to look for a prosaic, probably

messy laboratory which people who make a sport of hunting

fellow-humans won't find amusing. Characters like these, Murgatroyd,

aren't interested in medical science. They consider themselves

conquerors. People have strange ideas!"

"_Chee!_" said Murgatroyd.

Calhoun spread out his photographs. Kim Walpole had marked where he

should go and a route to it. Having been in the city while it was

building, he knew even the service-lanes which, being sunken, were not

a part of the city's good looks.

"But our enemies," explained Calhoun, "will not deign to use such

grubby routes. They consider themselves aristocrats because they were

sent as conquerors, whose job it was to clean up the dead bodies

of their victims. I wonder what kind of swine are in power in the

planetary government which sent them?"

* * * * *

He put away the photos and headed for the city again. He branched off

from the rural highway where a turn-off descended into a cut. This

low-level road was intended for loads of agricultural produce entering

the city. It was strictly utilitarian. It ran below the surface of the

park areas and entered the city without pride. It wound between rows of

service-gates, behind which waste matter was some day to be assembled

to be carted away for fertilizer on the fields. The city was very well

designed.

Rolling along the echoing sunken road, Calhoun saw, just once, a

ground-car in motion on a far-flung, cobwebby bridge between two tall

towers. It was high overhead. Nobody in it would be watching grubby

commerce-roads.

The whole affair was very simple indeed. Calhoun brought the car to a

stop beneath the overhang of a balconied building many stories high.

He got out and opened the gate. He drove the car into the cavernous,

so-far-unused lower part of the building. He closed the gate behind

him. He was in the center of the city, and his presence was unknown.

He climbed a new-clean flight of steps and came to the sections the

public would use. There were glassy walls which changed their look as

one moved between them. There were the lifts. Calhoun did not try to

use them. He led Murgatroyd up the circular ramps which led upward in

case of unthinkable emergency. He and Murgatroyd plodded up and up.

Calhoun kept count.

On the fifth level there were signs of use, while all the others had

that dusty cleanness of a structure which has been completed but not

yet occupied.

"Here we are," said Calhoun cheerfully.

But he had his blaster in his hand when he opened the door of the

laboratory. It was empty. He looked approvingly about as he hunted for

the storeroom. It was a perfectly equipped biological laboratory, and

it had been in use. Here the few doomed physicians awaiting the city's

population had worked desperately against the plague. Calhoun saw the

trays of cultures they'd made--dried up and dead, now. Somebody had

turned over a chair. Probably when the laboratory was searched by the

invaders, lest someone not of their kind remained alive in it.

He found the storeroom. Murgatroyd watched with bright eyes as he

rummaged.

"Here we have the things men use to cure each other," said Calhoun

oracularly. "Practically every one a poison save for its special use!

Here's an assortment of spores--pathogenic organisms, Murgatroyd.

One could start a plague with them. And here are drugs which are

synthesized nowadays, but are descended from the compounds found on

the spears of savages. Great helps in medicine. And here are the

anaesthetics--poisons, too. These are what I am counting on!"

He chose, very painstakingly. Dextrethyl. Polysulfate. The one marked

inflammable and dangerous. The other with the maximum permissible dose

on its label, and the name of counteracting substances which would

neutralize it. He burdened himself. Murgatroyd reached up a paw. Since

Calhoun was carrying something, he wanted to carry something, too.

They went down the circular ramp again. Calhoun searched once more in

the below-surface levels of the building. He found what he wanted--a

painter's vortex gun which would throw "smoke rings" of tiny

paint-droplets at a wall or object to be painted. One could vary the

size of the ring at impact from a bare inch to a three-foot spread.

Calhoun cleaned the paint gun. He was meticulous about it. He filled

its tank with dextrethyl brought down from the laboratory. He piled the

empty containers out of sight.

"This trick," he observed, as he picked up the paint gun again, "was

devised to be used on a poor devil of a lunatic who carried a bomb in

his pocket for protection against imaginary assassins. It would have

devastated a quarter-mile circle, so he had to be handled gently."

He patted his pockets. He nodded.

"Now we go hunting--with an oversized atomizer loaded with dextrethyl.

I've polysulfate and an injector to secure each specimen I knock over.

Not too good, eh? But if I have to use a blaster I'll have failed."

He looked out a window at the sky. It was now late afternoon. He went

back to the gate to the service road. He went out and piously closed it

behind him. On foot, with many references to the photomaps, he began to

find his way toward the landing grid. It ought to be something like the

center of the invaders' location.

* * * * *

It was dark when he climbed other service stairs from the cellar of

another building. This was the communications center of the city.

It had been the key to the mopping-up process the invaders began on

landing. Its call board would show which apartments had communicators

in use. When such a call showed, a murder-party could be sent to

take care of the caller. Even after the first night, some individual

isolated folk might remain--perhaps unaware of what went on. So there

would be somebody on watch, just in case a dying man called for the

solace of a human voice while still he lived.

There was a man on watch. Calhoun saw a lighted room. Paint gun at the

ready, he moved very silently toward it. Murgatroyd padded faithfully

behind him.

Outside the door, Calhoun adjusted his curious weapon. He entered.

There was a man nodding in a chair before the lifeless board. When

Calhoun entered he raised his head and yawned. He turned.

Calhoun sprayed him with smoke rings--vortex rings. But the rings were

spinning fissiles of vaporized dextrethyl--that anaesthetic developed

from ethyl chloride some two hundred years before, and not yet bettered

for its special uses. One of its properties was that the faintest

whiff of its odor produced a reflex impulse to gasp. A second property

was that--like the ancient ethyl chloride--it was the quickest-acting

anaesthetic known.

The man by the call board saw Calhoun. His nostrils caught the odor of

dextrethyl. He gasped.

He fell unconscious.

Calhoun waited patiently until the dextrethyl was out of the way. It

was almost unique among vapors in that at room temperature it was

lighter than air. It rose toward the ceiling. Calhoun moved forward,

brought out the polysulfate injector, and bent over the unconscious

man. He did not touch him otherwise.

He turned and walked out of the room with Murgatroyd piously marching

behind him.

Outside, Calhoun said:

"As one medical man to another, maybe I shouldn't have done that! I

doubt these invaders have a competent physician among them. But even

he would be apt to think that that man had collapsed suddenly and

directly into the coma of the plague. That polysulfate's an assisting

anaesthetic. It's not used alone, because when you knock a man out with

it he stays out for days. It's used just below the quantity that would

affect a man, and then the least whiff of another anaesthetic puts him

under, and he can be brought out fast and he's better off all around.

But I've got this man knocked out! He'll stay unconscious for a week."