Clarence Rimbro had no objections to living in the only house on an uninhabited planet, any more than had any other of Earth's even trillion of inhabitants.

If someone had questioned him concerning possible objections, he would undoubtedly have stared blankly at the questioner. His house was much larger than any house could possibly be on Earth proper and much more modern. It had its independent air supply and water supply, ample food in its freezing compartments. It was isolated from the lifeless planet on which it was located by a force field, but the rooms were built about a five-acre farm (under glass, of course), which, in the planet's beneficent sunlight, grew flowers for pleasure and vegetables for health. It even supported a few chickens. It gave Mrs. Rimbro something to do with herself afternoons, and a place for the two little Rimbros to play when they were tired of indoors.

Furthermore, if one wanted to be on Earth proper; if one insisted on it; if one had to have people around and air one could breathe in the open or water to swim in, one had only to go out of the front door of the house.

So where was the difficulty?

Remember, too, that on the lifeless planet on which the Rimbro house was located there was complete silence except for the occasional monotonous effects of wind and rain. There was absolute privacy and the feeling of absolute ownership of two hundred million square miles of planetary surface.

Clarence Rimbro appreciated all that in his distant way. He was an accountant, skilled in handling very advanced computer models, precise in his manners and clothing, not much given to smiling beneath his thin, well-kept mustache and properly aware of his own worth. When he drove from work toward home, he passed the occasional dwelling place on Earth proper and he never ceased to stare at them with a certain smugness.

Well, either for business reasons or mental perversion, some people simply had to live on Earth proper. It was too bad for them. After all, Earth proper's soil had to supply the minerals and basic food supply for all the trillion of inhabitants (in fifty years, it would be two trillion) and space was at a premium. Houses on Earth proper just couldn 't be any bigger than that, and people who had to live in them had to adjust to the fact.

Even the process of entering his house had its mild pleasantness. He would enter the community twist place to which he was assigned (it looked, as did all such, like a rather stumpy obelisk), and there he would invariably find others waiting to use it. Still more would arrive before he reached the head of the line. It was a sociable time.

"How's your planet?" "How's yours?" The usual small talk. Sometimes someone would be having trouble. Machinery breakdowns or serious weather that would alter the terrain unfavorably. Not often.

But it passed the time. Then Rimbro would be at the head of the line; he would put his key into the slot; the proper combination would be punched; and he would be twisted into a new probability pattern; his own particular probability pattern; the one assigned to him when he married and became a producing citizen; a probability pattern in which life had never developed on Earth. And twisting to this particular lifeless Earth, he would walk into his own foyer.

Just like that.

He never worried about being in another probability. Why should he? He never gave it any thought. There were an infinite number of possible Earths. Each existed in its own niche; its own probability pattern. Since on a planet such as Earth there was, according to calculation, about a fifty-fifty chance of life's developing, half of all the possible Earths (still infinite, since half of infinity was infinity) possessed life, and half (still infinite) did not. And living on about three hundred billion of the unoccupied Earths were three hundred billion families, each with its own beautiful house, powered by the sun of that probability, and each securely at peace. The number of Earths so occupied grew by millions each day.

And then one day, Rimbro came home and Sandra (his wife) said to him, as he entered, "There's been the most peculiar noise."

Rimbro's eyebrows shot up and he looked closely at his wife. Except for a certain restlessness of her thin hands and a pale look about the corners of her tight mouth, she looked normal.

Rimbro said, still holding his topcoat halfway toward the servette that waited patiently for it, "Noise? What noise? I don't hear anything."

"It's stopped now," Sandra said. "Really, it was like a deep thumping or

rumble. You'd hear it a bit. Then it would stop. Then you'd hear it a bit and so on. I've never heard anything like it."

Rimbro surrendered his coat. "But that's quite impossible."

"I heard it."

"I'll look over the machinery," he mumbled. "Something may be wrong."

Nothing was, that his accountant's eyes could discover, and, with a shrug, he went to supper. He listened to the servettes hum busily about their different chores, watched one sweep up the plates and cutlery for disposal and recovery, then said, pursing his lips, "Maybe one of the servettes is out of order. I'll check them."

"It wasn't anything like that, Clarence."

Rimbro went to bed, without further concern over the matter, and wakened with his wife's hand clutching his shoulder. His hand went automatically to the contact patch that set the walls glowing. "What's the matter? What time is it?"

She shook her head. "Listen! Listen!"

Good Lord, thought Rimbro, there is a noise. A definite rumbling. It came and went.

"Earthquake?" he whispered. It did happen, of course, though, with all the planet to choose from, they could generally count on having avoided the faulted areas.

"All day long?" asked Sandra fretfully. "I think it's something else." And then she voiced the secret terror of every nervous householder. "I think there's someone on the planet with us. This Earth is inhabited."

Rimbro did the logical things. When morning came, he took his wife and children to his wife's mother. He himself took a day off and hurried to the Sector's Housing Bureau.

He was quite annoyed at all his.

Bill Ching of the Housing Bureau was short, jovial and proud of his part Mongolian ancestry. He thought probability patterns had solved every last one of humanity's problems. Alec Mishnoff, also of the Housing Bureau, thought probability patterns were a snare into which humanity had been hopelessly tempted. He had originally majored in archeology and had studied a variety of antiquarian subjects with which his delicately poised head was still crammed. His face managed to look sensitive despite overbearing eyebrows, and he lived with a pet notion that so far he had dared tell no one, though preoccupation with it had driven him out of archeology and into housing.

Ching was fond of saying, "The hell with Malthus!" It was almost a verbal trademark of his. "The hell with Malthus. We can't possibly overpopulate now. However frequently we double and redouble, Homo sapiens remains finite in number, and the uninhabited Earths remain infinite. And we don't have to put one house on each planet. We can put a hundred,

a thousand, a million. Plenty of room and plenty of power from each probability sun."

"More than one on a planet?" said Mishnoff sourly.

Ching knew exactly what he meant. When probability patterns had first been put to use, sole ownership of a planet had been powerful inducement for early settlers. It appealed to the snob and despot in every one. What man so poor, ran the slogan, as not to have an empire larger than Genghis Khan's? To introduce multiple settling now would outrage everyone.

Ching said, with a shrug, "All right, it would take psychological preparation. So what? That's what it took to start the whole deal in the first place."

"And food?" asked Mishnoff.

"You know we're putting hydroponic works and yeast plants in other probability patterns. And if we had to, we could cultivate their soil."

"Wearing space suits and importing oxygen."

"We could reduce carbon dioxide for oxygen till the plants got going and they'd do the job after that."

"Given a million years."

"Mishnoff, the trouble with you," Ching said, "is you read too many ancient history books. You're an obstructionist."

But Ching was too good-natured really to mean that, and Mishnoff continued to read books and to worry. Mishnoff longed for the day he could get up the courage necessary to see the Head of the Section and put right out in plain view-bang, like that-exactly what it was that was troubling him.

But now, a Mr. Clarence Rimbro faced them, perspiring slightly and toweringly angry at the fact that it had taken him the better part of two days to reach this far into the Bureau.

He reached his exposition's climax by saying, "And / say the planet is inhabited and I don't propose to stand for it."

Having listened to his story in full, Ching tried the soothing approach. He said, "Noise like that is probably just some natural phenomenon."

"What kind of natural phenomenon?" demanded Rimbro. "I want an investigation. If it's a natural phenomenon, I want to know what kind. I say the place is inhabited. It has life on it, by Heaven, and I'm not paying rent on a planet to share it. And with dinosaurs, from the sound of it."

"Come, Mr. Rimbro, how long have you lived on your Earth?"

"Fifteen and a half years."

"And has there ever been any evidence of life?"

"There is now, and, as a citizen with a production record classified as A-I, I demand an investigation."

"Of course we'll investigate, sir, but we just want to assure you now that everything is all right. Do you realize how carefully we select our probability patterns?"

"I'm an accountant. I have a pretty good idea," said Rimbro at once.

"Then surely you know our computers cannot fail us. They never pick a

probability which has been picked before. They can't possibly. And they're geared to select only probability patterns in which Earth has a carbon dioxide atmosphere, one in which plant life, and therefore animal life, has never developed. Because if plants had evolved, the carbon dioxide would have been reduced to oxygen. Do you understand?"

"I understand it all very well and I'm not here for lectures," said Rimbro. "I want an investigation out of you and nothing else. It is quite humiliating to think I may be sharing my world, my own world, with something or other, and I don't propose to endure it."

"No, of course not," muttered Ching, avoiding Mishnoff's sardonic glance. "We'll be there before night."

They were on their way to the twisting place with full equipment.

Mishnoff said, "I want to ask you something. Why do you go through that There's no need to worry, sir' routine? They always worry anyway. Where does it get you?"

"I've got to try. They shouldn 't worry," said Ching petulantly. "Ever hear of a carbon dioxide planet that was inhabited? Besides, Rimbro is the type that starts rumors. I can spot them. By the time he's through, if he's encouraged, he'll say his sun went nova."

"That happens sometimes," said Mishnoff.

"So? One house is wiped out and one family dies. See, you're an obstructionist. In the old times, the times you like, if there were a flood in China or someplace, thousands of people would die. And that's out of a population of a measly billion or two."

Mishnoff muttered, "How do you know the Rimbro planet doesn't have life on it?"

"Carbon dioxide atmosphere."

"But suppose-" It was no use. Mishnoff couldn't say it. He finished lamely, "Suppose plant and animal life develops that can live on carbon 2j dioxide."

"It's never been observed."

"In an infinite number of worlds, anything can happen." He finished that 1 in a whisper. "Everything must happen."

"Chances are one in a duodecillion," said Ching, shrugging.

They arrived at the twisting point then, and, having utilized the freight twist for their vehicle (thus sending it into the Rimbro storage area), they entered the Rimbro probability pattern themselves. First Ching, then Mishnoff.

"A nice house," said Ching, with satisfaction. "Very nice model. Good taste." "Hear anything?" asked Mishnoff.

"No."

Ching wandered into the garden. "Hey," he yelled. "Rhode Island Reds."

Mishnoff followed, looking up at the glass roof. The sun looked like the sun of a trillion other Earths.

He said absently, "There could be plant life, just starting out. The carbon dioxide might just be starting to drop in concentration. The computer would never know."

"And it would take millions of years for animal life to begin and millions more for it to come out of the sea."

"It doesn't have to follow that pattern."

Ching put an arm about his partner's shoulder. "You brood. Someday, you'll tell me what's really bothering you, instead of just hinting, and we can straighten you out."

Mishnoff shrugged off the encircling arm with an annoyed frown. Ching's tolerance was always hard to bear. He began, "Let's not psychothera-pize-" He broke off, then whispered, "Listen."

There was a distant rumble. Again.

They placed the seismograph in the center of the room and activated the force field that penetrated downward and bound it rigidly to bedrock. They watched the quivering needle record the shocks.

Mishnoff said, "Surface waves only. Very superficial. It's not underground."

Ching looked a little more dismal, "What is it then?"

"1 think," said Mishnoff, "we'd better find out." His face was gray with apprehension. "We'll have to set up a seismograph at another point and get a fix on the focus of the disturbance."

"Obviously," said Ching. "I'll go out with the other seismograph. You stay here."

"No," said Mishnoff, with energy. "/'// go out."

Mishnoff felt terrified, but he had no choice. If this were it, he would be prepared. He could get a warning through. Sending out an unsuspecting Ching would be disastrous. Nor could he warn Ching, who would certainly never believe him.

But since Mishnoff was not cast in the heroic mold, he trembled as he got into his oxygen suit and fumbled the disrupter as he tried to dissolve the force field locally in order to free the emergency exit.

"Any reason you want to go, particularly?" asked Ching, watching the other's inept manipulations. "I'm willing."

"It's all right. I'm going out," said Mishnoff, out of a dry throat, and stepped into the lock that led out onto the desolate surface of a lifeless Earth. A presumably lifeless Earth.

The sight was not unfamiliar to Mishnoff. He had seen its like dozens of times. Bare rock, weathered by wind and rain, crusted and powdered with

sand in the gullies; a small and noisy brook beating itself against its stony course. All brown and gray; no sign of green. No sound of life.

Yet the sun was the same and, when night fell, the constellations would be the same.

The situation of the dwelling place was in that region which on Earth proper would be called Labrador. (It was Labrador here, too, really. It had been calculated that in not more than one out of a quadrillion or so Earths were there significant changes in the geological development. The continents were everywhere recognizable down to quite small details.)

Despite the situation and the time of the year, which was October, the temperature was sticky warm due to the hothouse effect of the carbon dioxide in this Earth's dead atmosphere.

From inside his suit, through the transparent visor, Mishnoff watched it all somberly. If the epicenter of the noise were close by, adjusting the second seismograph a mile or so away would be enough for the fix. If it weren't, they would have to bring in an air scooter. Well, assume the lesser complication to begin with.

Methodically, he made his way up a rocky hillside. Once at the top, he could choose his spot.

Once at the top, puffing and feeling the heat most unpleasantly, he found he didn't have to.

His heart was pounding so that he could scarcely hear his own voice as he yelled into his radio mouthpiece, "Hey, Ching, there's construction going on."

"What?" came back the appalled shout in his ears.

There was no mistake. Ground was being leveled. Machinery was at work. Rock was being blasted out.

Mishnoff shouted, "They're blasting. That's the noise."

Ching called back, "But it's impossible. The computer would never pick the same probability pattern twice. It couldn 't."

"You don't understand-" began Mishnoff.

But Ching was following his own thought processes. "Get over there, Mishnoff. I'm coming out, too."

"No, damn it. You stay there," cried Mishnoff in alarm. "Keep me in radio contact, and for God's sake be ready to leave for Earth proper on wings if I give the word."

"Why?" demanded Ching. "What's going on?"

"I don't know yet," said Mishnoff. "Give me a chance to find out."

To his own surprise, he noticed his teeth were chattering.

Muttering breathless curses at the computer, at probability patterns and at the insatiable need for living space on the part of a trillion human beings expanding in numbers like a puff of smoke, Mishnoff slithered and slipped down the other side of the slope, setting stones to rolling and rousing peculiar echoes.

A man came out to meet him, dressed in a gas-tight suit, different in many details from Mishnoff's own, but obviously intended for the same purpose-to lead oxygen to the lungs.

Mishnoff gasped breathlessly into his mouthpiece, "Hold it, Ching. There's a man coming. Keep in touch." Mishnoff felt his heart pump more easily and the bellows of his lungs labor less.

The two men were staring at one another. The other man was blond and craggy of face. The look of surprise about him was too extreme to be feigned.

He said in a harsh voice, "Wer sind Sie? Was machen Sie hier?"

Mishnoff was thunderstruck. He'd studied ancient German for two years in the days when he expected to be an archeologist and he followed the comment despite the fact that the pronunciation was not what he had been taught. The stranger was asking his identity and his business there.

Stupidly, Mishnoff stammered, "Sprechen Sie Deutsch?"and then had to mutter reassurance to Ching whose agitated voice in his earpiece was demanding to know what the gibberish was all about.

The German-speaking one made no direct answer. He repeated, "Wer sind Sie?" and added impatiently, "Hier ist fiir ein verriickten Spass keine Zeit."

Mishnoff didn't feel like a joke either, particularly not a foolish one, but he continued, "Sprechen Sie Planetisch?"

He did not know the German for "Planetary Standard Language" so he had to guess. Too late, he thought he should have referred to it simply as English.

The other man stared wide-eyed at him. "Sind Sie wahnsinnig?"

Mishnoff was almost willing to settle for that, but in feeble self-defense, he said, "I'm not crazy, damn it. I mean, "AufderErde woher Sie gekom-"

He gave it up for lack of German, but the new idea that was rattling inside his skull would not quit its nagging. He had to find some way of testing it. He said desperately, "Welches fahr ist es jetzt?"

Presumably, the stranger, who was questioning his sanity already, would be convinced of Mishnoff's insanity now that he was being asked what year it was, but it was one question for which Mishnoff had the necessary German.

The other muttered something that sounded suspiciously like good German swearing and then said, "Es ist dock zwei tausend drei hundert vier-und-sechzig, und warum-"

The stream of German that followed was completely incomprehensible to Mishnoff, but in any case he had had enough for the moment. If he translated the German correctly, the year given him was 2364, which was nearly two thousand years in the past. How could that be?

He muttered, "Zwei tausend drei hundert vier-und sechzig?"

"/a, fa," said the other, with deep sarcasm. "Zwei tausend drei hundert vier-und-sechzig. Der ganze fahr long ist es so gewesen."

Mishnoff shrugged. The statement that it had been so all year long was a feeble witticism even in German and it gained nothing in translation. He pondered.

But then the other's ironical tone deepening, the German-speaking one went on, "Zwei tausend drei hundert vier-und-sechzig nach Hitler. Hilft das Ihnen vielleicht? Nach Hitler!"

Mishnoff yelled with delight. "That does help me. Es hilft! Horen Sie, bitte-" He went on in broken German interspersed with scraps of Planetary, "For Heaven's sake, urn Gottes willen-"

Making it 2364 after Hitler was different altogether.

He put German together desperately, trying to explain.

The other frowned and grew thoughtful. He lifted his gloved hand to stroke his chin or make some equivalent gesture, hit the transparent visor that covered his face and left his hand there uselessly, while he thought.

He said, suddenly, "Ich heiss George Fallenby."

To Mishnoff it seemed that the name must be of Anglo-Saxon derivation, although the change in vowel form as pronounced by the other made it seem Teutonic.

"Guten Tag," said Mishnoff awkwardly. "Ich heiss Alec Mishnoff," and was suddenly aware of the Slavic derivation of his own name.

"Kommen Sie mit mir, Hen Mishnoff," said Fallenby.

Mishnoff followed with a strained smile, muttering into his transmitter, "It's all right, Ching. It's all right."

Back on Earth proper, Mishnoff faced the Sector's Bureau Head, who had grown old in the Service; whose every gray hair betokened a problem met and solved; and every missing hair a problem averted. He was a cautious man with eyes still bright and teeth that were still his own. His name was Berg.

He shook his head. "And they speak German: but the German you studied was two thousand years old."

"True," said Mishnoff. "But the English Hemingway used is two thousand years old and Planetary is close enough for anyone to be able to read it."

"Hmp. And who's this Hitler?"

"He was a sort of tribal chief in ancient times. He led the German tribe in one of the wars of the twentieth century, just about the time the Atomic Age started and true history began."

"Before the Devastation, you mean?"

"Right. There was a series of wars then. The Anglo-Saxon countries won out, and I suppose that's why the Earth speaks Planetary."

"And if Hitler and his Germans had won out, the world would speak German instead?"

"They have won out on Fallenby's Earth, sir, and they do speak German."

"And make their dates 'after Hitler' instead of a.d.?"

"Right. And I suppose there's an Earth in which the Slavic tribes won out and everyone speaks Russian."

"Somehow," said Berg, "it seems to me we should have foreseen it, and yet, as far as I know, no one has. After all, there are an infinite number of inhabited Earths, and we can't be the only one that has decided to solve the problem of unlimited population growth by expanding into the worlds of probability."

"Exactly," said Mishnoff earnestly, "and it seems to me that if you think of it, there must be countless inhabited Earths so doing and there must be many multiple occupations in the three hundred billion Earths we ourselves occupy. The only reason we caught this one is that, by sheer chance, they decided to build within a mile of the dwelling we had placed there. This is something we must check."

"You imply we ought to search all our Earths."

"I do, sir. We've got to make some settlement with other inhabited Earths. After all, there is room for all of us and to expand without agreement may result in all sorts of trouble and conflict."

"Yes," said Berg thoughtfully. "1 agree with you."

Clarence Rimbro stared suspiciously at Berg's old face, creased now into all manner of benevolence.

"You're sure now?"

"Absolutely," said the Bureau Head. "We're sorry that you've had to accept temporary quarters for the last two weeks-"

"More like three."

"-three weeks, but you will be compensated."

"What was the noise?"

"Purely geological, sir. A rock was delicately balanced and, with the wind, it made occasional contact with the rocks of the hillside. We've removed it and surveyed the area to make certain that nothing similar will occur again."

Rimbro clutched his hat and said, "Well, thanks for your trouble."

"No thanks necessary, I assure you, Mr. Rimbro. This is our job."

Rimbro was ushered out, and Berg turned to Mishnoff, who had remained a quiet spectator of this completion of the Rimbro affair.

Berg said, "The Germans were nice about it, anyway. They admitted we had priority and got off. Room for everybody, they said. Of course, as it turned out, they build any number of dwellings on each unoccupied world. . . . And now there's the project of surveying our other worlds and making similar agreements with whomever we find. It's all strictly confidential, too.

It can't be made known to the populace without plenty of preparation. . . . Still, none of this is what I want to speak to you about."

"Oh?" said Mishnoff. Developments had not noticeably cheered him. His own bogey still concerned him.

Berg smiled at the younger man. "You understand, Mishnoff, we in the Bureau, and in the Planetary Government, too, are very appreciative of your quick thinking, of your understanding of the situation. This could have developed into something very tragic, had it not been for you. This appreciation will take some tangible form."

"Thank you, sir."

"But, as I said once before, this is something many of us should have thought of. How is it you did? . . . Now we've gone into your background a little. Your co-worker, Ching, tells us you have hinted in the past at some serious danger involved in our probability-pattern setup, and that you insisted on going out to meet the Germans although you were obviously frightened. You were anticipating what you actually found, were you not? And how did you do it?"

Mishnoff said confusedly, "No, no. That was not in my mind at all. It came as a surprise. I-"

Suddenly he stiffened. Why not now? They were grateful to him. He had proved that he was a man to be taken into account. One unexpected thing had already happened.

He said firmly, "There's something else."

"Yes?"

(How did one begin?) "There's no life in the Solar System other than the life on Earth."

"That's right," said Berg benevolently.

"And computation has it that the probability of developing any form of interstellar travel is so low as to be infinitesimal."

"What are you getting at?"

"That all this is so in this probability! But there must be some probability patterns in which other life does exist in the Solar System or in which interstellar drives are developed by dwellers in other star systems."

Berg frowned. "Theoretically."

"In one of these probabilities, Earth may be visited by such intelligences. If it were a probability pattern in which Earth is inhabited, it won't affect us; they'll have no connection with us in Earth proper. But if it were a probability pattern in which Earth is uninhabited and they set up some sort of a base, they may find, by happenstance, one of our dwelling places."

"Why ours?" demanded Berg dryly. "What not a dwelling place of the Germans, for instance?"

"Because we spot our dwellings one to a world. The German Earth doesn't. Probably very few others do. The odds are in favor of us by billions

to one. And if extraterrestrials do find such a dwelling, they'll investigate and find the route to Earth proper, a highly developed, rich world."

"Not if we turn off the twisting place," said Berg.

"Once they know that twisting places exist, they can construct their own," said Mishnoff. "A race intelligent enough to travel through space could do that, and from the equipment in the dwelling they would take over, they could easily spot our particular probability. . . . And then how would we handle extraterrestrials? They're not Germans, or other Earths. They would have alien psychologies and motivations. And we're not even on our guard. We just keep setting up more and more worlds and increasing the chance every day that-"

His voice had risen in excitement and Berg shouted at him, "Nonsense. This is all ridiculous-"

The buzzer sounded and the communiplate brightened and showed the face of Ching. Ching's voice said, "I'm sorry to interrupt, but-"

"What is it?" demanded Berg savagely.

"There's a man here I don't know what to do with. He's drunk or crazy. He complains that his home is surrounded and that there are things staring through the glass roof of his garden."

"Things?" cried Mishnoff.

"Purple things with big red veins, three eyes and some sort of tentacles instead of hair. They have-"

But Mishnoff and Berg didn't hear the rest. They were staring at each other in sick horror.