It was almost a class reunion, and though it was marked by joylessness, there was no reason as yet to think it would be marred by tragedy.

Edward Talliaferro, fresh from the Moon and without his gravity legs yet, met the other two in Stanley Kaunas' room. Kaunas rose to greet him in a subdued manner. Battersley Ryger merely sat and nodded.

Talliaferro lowered his large body carefully to the couch, very aware of its unaccustomed weight. He grimaced a little, his plump lips twisting inside the rim of hair that surrounded them on lip, chin, and cheek.

They had seen one another earlier that day under more formal conditions. Now for the first time they were alone and Talliaferro said, This is a kind of occasion. We're meeting for the first time in ten years. First time since graduation, in fact.'

Ryger's nose twitched. It had been broken shortly before that same graduation and he had received his degree in astronomy with a bandage disfiguring his face. He said grumpily, 'Anyone ordered champagne?

Or something?'

Talliaferro said, 'Come on! First big interplanetary astronomical convention in history is no place for glooming. And among friends, too!'

Kaunas said suddenly, 'It's Earth. It doesn't feel right. I can't get used to it.' He shook his head but his look of depression remained.

Talliaferro said, 'I know. I'm so heavy. It takes all the energy out of me. At that, you're better off than I am, Kaunas. Mercurian gravity is 0-4 normal. On the Moon, it's only 0 - I6.' He interrupted Ryger's beginning of a sound by saying, 'And on Ceres they use pseudo-grav fields adjusted to 0-8. You have no problems at all, Ryger.'

The Cerian astronomer looked annoyed. 'It's the open air. Going outside without a suit gets me.'

'Right,' agreed Kaunas. 'And letting the Sun beat down on you. Just letting it.'

Talliaferro found himself insensibly drifting back in time. They had not changed much. Nor, he thought, had he himself. They were all ten years older, of course. Ryger had put on some weight and Kaunas' thin face had grown a bit leathery, but he would have recognized either if he had met him without warning.

He said, 'I don't think it's Earth getting us. Let's face it.'

Kaunas looked up sharply. He was a little fellow with quick, nervous movements of his hands and habitually wore clothes that looked a shade too large for him.

He said, 'Villiers! I know. I think about him sometimes.' Then, with an air of desperation, 'I got a letter from him.'

Ryger sat upright, his olive complexion darkening further, and said with energy, 'You did? When?'

'A month ago.'

Ryger turned to Talliaferro. 'How about you?' Talliaferro blinked placidly and nodded.

Ryger said, 'He's gone crazy. He claims he's discovered a practical method of mass transference through space. -He told you two also? -That's it, then. He was always a little bent. Now he's broken.'

He rubbed his nose fiercely, and Talliaferro thought of the day Villiers had broken it.

For ten years Villiers had haunted them like the vague shadow of a guilt that wasn't really theirs. They had gone through their graduate work together, four picked and dedicated men being trained for a profession that had reached new heights in this age of interplanetary travel.

The observatories were opening on the other worlds, surrounded by vacuum, unblurred by air.

There was the Lunar Observatory, from which Earth and the inner planets could be studied; a silent world in whose sky the home planet hung suspended.

Mercury Observatory, closest to the Sun, perched at Mercury's north pole, where the terminator moved scarcely at all, and the Sun was fixed on the horizon and could be studied in the minutest detail.

Ceres Observatory, newest, most modern, with its range extending from Jupiter to the outermost galaxies.

There were disadvantages, of course. With interplanetary travel still difficult, leaves would be few, anything like normal life virtually impossible, but this was a lucky.generation. Coming scientists would find the fields of knowledge well reaped and, until the invention of an interstellar drive, no new horizon as capacious as this one would be opened.

These lucky four, Talliaferro, Ryger, Kaunas, and Villiers, were to be in the position of a Galileo, who, by virtue of owning the first real telescope, could not point it anywhere in the sky without making a major discovery.

But then Romano Villiers had fallen sick and it was rheumatic fever. Whose fault was that? His heart had been left leaking and limping.

He was the most brilliant of the four, the most hopeful, the most intense-and he could not even finish his schooling and get his doctorate.

Worse than that, he could never leave Earth; the acceleration of a spaceship's takeoff would kill him. Talliaferro was marked for the Moon, Ryger for Ceres, Kaunas for Mercury. Only Villiers stayed behind, a life prisoner of Earth.

They had tried telling their pity and Villiers had rejected it with something approaching hate. He had railed at them and cursed them. When Ryger lost his temper and lifted his fist, Villiers had sprung at him screaming and broken his nose.

Obviously Ryger hadn't forgotten that, as he caressed his nose gingerly with one finger.

Kaunas' forehead was an uncertain washboard of wrinkles. 'He's at the Convention, you know. He's got a room in the hotel-405.'

'I won't see him,' said Ryger.

'He's coming up here. He said he wanted to see us. I thought he said nine. He'll be here any minute.'

'In that case,' said Ryger, 'if you don't mind, I'm leaving.'

Talliaferro said, 'Oh, wait awhile. What's the harm in seeing him?'

'Because there's no point. He's insane.'

'Even so. Let's not be petty about it. Are you afraid of him?'

'Afraid!' Ryger looked contemptuous.

'Nervous, then. What is there to be so nervous about?'

'I'm not nervous,' said Ryger.

'Sure you are. We all feel guilty about him, and without real reason. Nothing that happened was our fault.' But he was speaking defensively and he knew it.

And when, at that point, the door signal sounded, all three jumped and turned to stare uneasily at the barrier that stood between themselves and Villiers.

The door opened and Romano Villiers walked in. The others rose stiffly to greet him, then remained standing in embarrassment, without one hand being raised.

He stared them down sardonically.

He's changed, thought Talliaferro.

He had. He had shrunk in almost every dimension. A gathering stoop even made him seem shorter. The skin of his scalp glistened through thinning hair, the skin on the back of his hands was ridged crookedly with bluish veins. He looked ill. There seemed nothing to link him to the memory of the past except for his trick of shading his eyes with one hand when he stared intently and, when he spoke, the even, controlled baritone of his voice.

He said. 'My friends! My space-trotting friends! We've lost touch.'

Talliaferro said, 'Hello Villiers.' Villiers eyed him. 'Are you well?'

'Well enough.'

'And you two?'

Kaunas managed a weak smile and a murmur. Ryger snapped, 'All right, Villiers. What's up?'

'Ryger, the angry man,' said Villiers. 'How's Ceres?'

'It was doing well when I left. How's Earth?'

'You can see for yourself,' but Villiers tightened as he said that.

He went on, 'I am hoping that the reason all three of you have come to the Convention is to hear my paper day after tomorrow.'

'Your paper? What paper?' asked Talliaferro.

'I wrote you all about it. My method of mass transference.'

Ryger smiled with one corner of his mouth. 'Yes, you did. You didn't say anything about a paper, though, and I don't recall that you're listed as one of the speakers. I would have noticed it if you had been.'

'You're right. I'm not listed. Nor have I prepared an abstract for publication.'

Villiers had flushed and Talliaferro said soothingly, 'Take it easy, Villiers. You don't look well.' Villiers whirled on him, lips contorted. 'My heart's holding out, thank you.'

Kaunas said, 'Listen, Villiers, if you're not listed or abstracted-'

'You listen. I've waited ten years. You have the jobs in space and I have to teach school on Earth, but

I'm a better man than any of you or all of you.'

'Granted-' began Talliaferro.

'And I don't want your condescension, either. Mandel witnessed it. I suppose you've heard of Mandel. Well, he's chairman of the astronautics division at the Convention and I demonstrated mass transference for him. It was a crude device and it burned out after one use but- Are you listening?'

'We're listening,' said Ryger coldly. 'For what that counts.'

'He'll let me talk about it my way. You bet he will. No warning. No advertisement. I'm going to spring it at them like a bombshell. When I give them the fundamental relationships involved it will break up the

Convention. They'll scatter to their home labs to check on me and builddevices. And they'll find it works.

I made a five mousedisappear at one spot in my lab and appear in another. Mandelwitnessed it.'

He stared at them, glaring first at one face, then at another. He said, 'You don't believe me, do you?' Ryger said, 'If you don't want advertisement, why do yon tell us?'

'You're different. You're my friends, my classmates. Youwent out into space and left me behind.'

'That wasn't a matter of choice,' objected Kaunas in a thin, high voice.

Villiers ignored that. He said, 'So I want you to know now. What will work for a mouse will work for a human. What will move something ten feet across a lab will move it a million miles across space. I'll be on the Moon, and on Mercury, and on Ceres and anywhere I want to go. I'll match every one of you and more. And I'll have done more for astronomy just teaching school and thinking than all of you with your observatories and telescopes and cameras and spaceships.'

'Well,' said Talliaferro, 'I'm pleased. More power to you. May I see a copy of the paper?'

'Oh, no.' Villiers' hands clenched close to his chest as though he were holding phantom sheets and shielding them from observation. 'You wait like everyone else. There's only one copy and no one will see it till I'm ready. Not even Mandel.'

'One copy!' cried Talliaferro. 'If you misplace it-'

'I won't. And if I do, it's all in my head.'

'If you-' Talliaferro almost finished that sentence with 'die' but stopped himself. Instead, he went on after an almost imperceptible pause, '-have any sense, you'll scan it at least. For safety's sake.'

'No,' said Villiers shortly. 'You'll hear me day after tomorrow. You'll see the human horizon expanded at one stroke as it never has been before.'

Again he stared intently at each face. Ten years,' he said. 'Good-bye.'

'He's mad,' said Ryger explosively, staring at the door as though Villiers were still standing before it.

'Is he?' said Talliaferro thoughtfully. 'I suppose he is, in a way. He hates us for irrational reasons. And, then, not even to scan his paper as a precaution...'

Talliaferro fingered his own small scanner as he said that. It was just a neutrally colored, undistinguished cylinder, somewhat thicker and somewhat shorter than an ordinary pencil. In recent years it had become the hallmark of the scientist, much as the stethoscope was that of the physician and the microcomputer that of the statistician. The scanner was worn in a jacket pocket, or clipped to a sleeve, or slipped behind the ear or swung at the end of a string.

Talliaferro sometimes, in his more philosophical moments, wondered how it was in the days when research men had to make laborious notes of the literature or file away full-sized reprints. How unwieldy!

Now it was only necessary to scan anything printed or written to have a micronegative which could be developed at leisure. Talliaferro had already recorded every abstract included in the program booklet of the Convention. The other two, he assumed with full confidence, had done likewise. Talliaferro said, 'Under the circumstances, refusal to scan is mad.'

'Space!' said Ryger hotly. 'There is no paper. There is no discovery. Scoring one on us would be worth any lie to him.'

'But then what will he do day after tomorrow?' asked Kaunas.

'How do I know? He's a madman.'

Talliaferro still played with his scanner and wondered idly if he ought to remove and develop some of the small slivers of film that lay stored away in its vitals. He decided against it. He said, 'Don't underestimate Villiers. He's a brain.'

Ten years ago, maybe,' said Ryger. 'Now he's a nut. I propose we forget him.'

He spoke loudly, as though to drive away Villiers and all that concerned him by the sheer force with which he discussed other things. He talked about Ceres and his work- the radio plotting of the Milky Way with new radioscopes capable of the resolution of single stars.

Kaunas listened and nodded, then chimed in with information concerning the radio emissions of sunspots and his own paper, in press, on the association of proton storms with the gigantic hydrogen flares on the Sun's surface.

Talliaferro contributed little. Lunar work was unglamorous in comparison. The latest information on long-scale weather forecasting through direct observation of terrestrial jet streams would not compare with radioscopes and protonstorms.

More than that, his thoughts could not leave Villers. Villiers was the brain. They all knew it. Even Ryger, for all his bluster, must feel that if mass transference were at all possible then Villiers was a logical discoverer.

The discussion of their own work amounted to no more than an uneasy admission that none of them had come to much. Talliaferro had followed the literature and knew. His own papers had been minor. The others had authored nothing of great importance.

None of them-face the fact-had developed into space shakers. The colossal dreams of schooldays had not come true and that was that. They were competent routine workmen. No more than that, they knew.

Villiers would have been more. They knew that, too. It was that knowledge, as well as guilt, which kept them in antagonism.

Talliaferro felt uneasily that Villiers, despite everything, was yet to be more. The others must be thinking so too, and mediocrity could grow quickly unbearable. The mass transference paper would come to pass and Villiers would be the great man after all, as he was always fated to be apparently, while his classmates, with all their advantages, would be forgotten. Their role would be no more than to applaud from the crowd.

He felt his own envy and chagrin and was ashamed of it, but felt it nonetheless.

Conversation died, and Kaunas said, his eyes turning away, 'Listen, why don't we drop in on old Villiers?'

There was a false heartiness about it, a completely unconvincing effort at casualness. He added, 'No use leaving bad feelings...'

Talliaferro thought. He wants to make sure about the mass transference. He's hoping it is only a madman's nightmare so he can sleep tonight.

But he was curious himself, so he made no objection, and even Ryger shrugged with ill grace and said,

'Hell, why not?'

It was then a little before eleven.

Talliaferro was awakened by the insistent ringing of his door signal. He hitched himself to one elbow in the darkness and felt distinctly outraged. The soft glow of the ceiling indicator showed it to be not quite four in the morning.

He cried out, 'Who is it?'

The ringing continued in spurts.

Growling, Talliaferro slipped into his bathrobe. He opened the door and blinked in the corridor light. He recognized the man who faced him from the trimensionals he had seen often enough.

Nevertheless the man said in an abrupt whisper, 'My name is Hubert Mandel.'

'Yes, sir,' said Talliaferro. Mandel was one of the Names in astronomy, prominent enough to have an important executive position with the World Astronomical Bureau, active enough to be Chairman of the astronautics section here at the Convention.

It suddenly struck Talliaferro that it was Mandel for whom Villiers claimed to have demonstrated mass transference. The thought of Villiers was somehow a sobering one.

Mandel said, 'You are Dr. Edward Talliaferro?'

'Yes, sir.'

Then dress and come with me. It is very important. It concerns a common acquaintance.'

'Dr. Villiers?'

Mandel's eyes flickered a bit. His brows and lashes were so fair as to give those eyes a naked, unfringed appearance. His hair was silky thin, his age about fifty.

He said, 'Why Villiers?'

'He mentioned you last evening. I don't know any other common acquaintance.'

Mandel nodded, waited for Talliaferro to finish slipping into his clothes, then turned and led the way. Ryger and Kaunas were waiting in a room one floor above Talliaferro's. Kaunas' eyes were red and troubled. Ryger was smoking a cigarette with impatient puffs.

Talliaferro said. 'We're all here. Another reunion.' It fell flat.

He took a seat and the three stared at one another. Ryger shrugged.

Mandel paced the floor, hands deep in his pockets. He said, 'I apologize for any inconvenience, gentlemen, and I thank you for your cooperation. I would like more of it. Our friend Romano Villiers is dead. About an hour ago, his body was removed from the hotel. The medical judgment is heart failure.'

There was a stunned silence. Ryger's cigarette hovered halfway to his lips, then sank slowly without completing its journey.

'Poor devil,' said Talliaferro.

'Horrible,' whispered Kaunas hoarsely. 'He was...' His voice played out. Ryger shook himself. 'Well, he had a bad heart. There's nothing to be done.'

'One little thing,' corrected Mandel quietly. 'Recovery.'

'What does that mean?' asked Ryger sharply. Mandel said, 'When did you three see him last?'

Talliaferro spoke. 'Last evening. It turned out to be a reunion. We all met for the first time in ten years. It wasn't a pleasant meeting, I'm sorry to say. Villiers felt he had cause for anger with us, and he was angry.'

That was-when?'

'About nine, the first time.' The first time?'

'We saw him again later in the evening.'

Kaunas looked troubled. 'He had stormed off angrily. We couldn't leave it at that. We had to try. It wasn't as if we hadn't all been friends at one time. So we went to his room and-'

Mandel pounced on that. 'You were all in his room?'

'Yes,' said Kaunas, surprised.

'About when?'

'Eleven, I think.' He looked at the others. Talliaferro nodded.

'And how long did you stay?'

'Two minutes,' put in Ryger. 'He ordered us out as though we were after his paper.' He paused as if expecting Mandel to ask what paper, but Mandel said nothing. He went on, 'I think he kept it under his pillow. At least he lay across the pillow as he yelled at us to leave.'

'He may have been dying then,' said Kaunas in a sick whisper.

'Not then,' said Mandel shortly. 'So you probably all left fingerprints.'

'Probably,' said Talliaferro. He was losing some of his automatic respect for Mandel and a sense of impatience was returning. It was four in the morning, Mandel or no. He said, 'Now what's all this about?'

'Well, gentlemen,' said Mandel, 'there's more to Villiers' death than the fact of death. Villiers' paper, the only copy of it as far as I know, was stuffed into the flash-disposal unit and only scraps of it were left.

I've never seen or read the paper, but I knew enough about the matter to be willing to swear in court if necessary that the remnants of unflashed paper in the disposal unit were of the paper he was planning to give at this Convention. You seem doubtful, Dr. Ryger.'

Ryger smiled sourly. 'Doubtful that he was going to give it. If you want my opinion, sir, he was mad. For ten years he was a prisoner of Earth and he fantasied mass transference as escape. It was all that kept him alive probably. He rigged up some sort of fraudulent demonstration. I don't say it was deliberate fraud. He was probably madly sincere, and sincerely mad. Last evening was the climax. He came to our rooms-he hated us for having escaped Earth-and triumphed over us. It was what he had lived for for ten years. It may have shocked him back to some form of sanity. He knew he couldn't actually give the paper; there was nothing to give. So he burned it and his heart gave out. It is too bad.'

Mandel listened to the Cerian astronomer, wearing a look of sharp disapproval. He said, 'Very glib, Dr. Ryger, but quite wrong. I am not so easily fooled by fraudulent demonstrations as you may believe. Now according to the registration data, which I have been forced to check rather hastily, you three were his classmates at college. Is that right?'

They nodded.

'Are there any other classmates of your present at the Convention?'

'No,' said Kaunas. 'We were the only four qualifying for a doctorate in astronomy that year. At least he would have qualified except-'

'Yes, I understand,' said Mandel. 'Well, then, in that case one of you three visited Villiers in his room one last time at midnight.'

There was a short silence. Then Ryger said coldly, 'Not I.' Kaunas, eyes wide, shook his head. Talliaferro said, 'What are you implying?'

'One of you came to him at midnight and insisted on seeing his paper. I don't know the motive.

Conceivably it was with the deliberate intention of forcing him into heart failure. When Villiers collapsed, the criminal, if I may call him so, was ready. He snatched the paper, which, I might add, probably was kept under his pillow, and scanned it. Then he destroyed the paper itself in the flash-disposal, but he was in a hurry and destruction wasn't complete.'

Ryger interrupted. 'How do you know all this? Were you a witness?'

'Almost,' said Mandel. 'Villiers was not quite dead at the moment of his first collapse. When the criminal left, he managed to reach the phone and call my room. He choked out a few phrases, enough to outline what had occurred. Unfortunately I was not in my room; a late conference kept me away. However, my recording attachment taped it. I always play the recording tape back whenever I return to my room or office. Bureaucratic habit. I called back. He was dead.'

'Well, then,' said Ryger, 'who did he say did it?'

'He didn't. Or if he did, it was unintelligible. But one word rang out clearly. It was classmate.' Talliaferro detached his scanner from its place in his inner jacket pocket and held it out toward Mandel. Quietly he said, 'If you would like to develop the film in my scanner, you are welcome to do so. You will not find Villiers' paper there.'

At once Kaunas did the same, and Ryger, with a scowl, joined.

Mandel took all three scanners and said dryly, 'Presumably, whichever one of you has done this has already disposed of the piece of exposed film with the paper on it. However-'

Talliaferro raised his eyebrows. 'You may search my person or my room.'

But Ryger was still scowling. 'Now wait a minute, wait one bloody minute. Are you the police?'

Mandel stared at him. 'Do you want the police? Do you want a scandal and a murder charge? Do you want the Convention disrupted and the System press making a holiday out of astronomy and astronomers? Villiers' death might well have been accidental. He did have a bad heart. Whichever one of you was there may well have acted on impulse. It may not have been a premeditated crime. If whoever it is will return the negative, we can avoid a great deal of trouble.'

'Even for the criminal?' asked Talliaferro.

Mandel shrugged. There may be trouble for him. I will not promise immunity. But whatever the trouble, it won't be public disgrace and life imprisonment, as it might be if the police are called in.'

Silence.

Mandel said, 'It is one of you three.' Silence.

Mandel went on, 'I think I can see the original reasoning of the guilty person. The paper would be destroyed. Only we four knew of the mass transference and only I had ever seen a demonstration. Moreover you had only his word, a madman's word perhaps, that I had seen it. With Villiers dead of heart failure and the paper gone, it would be easy to believe Dr. Ryger's theory that there was no mass transference and never had been. A year or two might pass and our criminal, in possession of the mass transference data, could reveal it little by little, rig experiments, publish careful papers, and end as the apparent discoverer with all that would imply in terms of money and renown. Even his own classmates would suspect nothing. At most they would believe that the long-past affair with Villiers had inspired him to begin investigations in the field. No more.'

Mandel looked sharply from one face to another, 'But none of that will work now. Any of the three of you who comes through with mass transference is proclaiming himself the criminal. I've seen the demonstration; I know it is legitimate; I know that one of you possesses a record of the paper. The information is therefore useless to you. Give it up then.'

Silence.

Mandel walked to the door and turned again. 'I'd appreciate it if you would stay here till I return. I won't be long. I hope the guilty one will use the interval to consider. If he's afraid a confession will lose him his job, let him remember that a session with the police may lose him his liberty and cost him the psychoprobe.' He hefted the three scanners, looked grim and somewhat in need of sleep. 'I'll develop these.'

Kaunas tried to smile. 'What if we make a break for it while you're gone?'

'Only one of you has reason to try,' said Mandel. 'I think I can rely on the two innocent ones to control the third, if only out of self-protection.' He left.

It was five in the morning. Ryger looked at his watch indignantly. 'A hell of a thing. I want to sleep.'

'We can curl up here,' said Talliaferro philosophically. 'Is anyone planning a confession?' Kaunas looked away and Ryger's lip lifted.

'I didn't think so.' Talliaferro closed his eyes, leaned his large head back against the chair, and said in a tired voice, 'Back on the Moon, they're in the slack season. We've got a two-week night and then it's busy, busy. Then there's two weeks of Sun and there's nothing but calculations, correlations, and bull sessions. That's the hard time. I hate it. If there were more women, if I could arrange something permanent...'

In a whisper, Kaunas talked about the fact that it was still impossible to get the entire Sun above the horizon and in view of the telescope on Mercury. But, with another two miles of track soon to be laid down for the observatory- move the whole thing, you know, tremendous forces involved, solar energy used directly-it might be managed. It would be managed.

Even Ryger consented to talk of Ceres after listening to the low murmur of the other voices. There was the problem there of the two-hour rotation period, which meant the stars whipped across the sky at an angular velocity twelve times that in Earth's sky. A net of three light scopes, three radioscopes, three of everything, caught the fields of study from one another as they whirled past.

'Could you use one of the poles?' asked Kaunas.

'You're thinking of Mercury and the Sun,' said Ryger, impatiently. 'Even at the poles the sky would still twist, and half of it would be forever hidden. Now if Ceres showed only one face to the Sun, the way Mercury does, we could have a permanent night sky with the stars rotating slowly once in three years.'

The sky lightened and it dawned slowly.

Talliaferro was half-asleep, but he kept hold of half-consciousness firmly. He would not fall asleep and leave the others awake. Each of the three, he thought, was wondering, 'Who? Who?'

Except the guilty one, of course.

Talliaferro's eyes snapped open as Mandel entered again. The sky, as seen from the window, had grown blue. Talliaferro was glad the window was closed. The hotel was air-conditioned, of course, but windows would be opened during the mild seasons of the year by those Earthmen who fancied the illusion of fresh air. Talliaferro, with Moon vacuum on his mind, shuddered at the thought with real discomfort.

Mandel said, 'Have any of you anything to say?' They looked at him steadily. Ryger shook his head.

Mandel said, 'I have developed the film in your scanners, gentlemen, and viewed the results.' He tossed scanners and developed slivers of film on to the bed. 'Nothing! You'll have trouble sorting out the film, I'm afraid. For that I'm sorry. And now there is still the question of the missing film.'

'If any,' said Ryger, and yawned prodigiously.

Mandel said, 'I would suggest we come down to Villiers' room, gentlemen.' Kaunas looked startled. 'Why?'

Talliaferro said. 'Is this psychology? Bring the criminal to the scene of the crime and remorse will wring a confession from him?'

Mandel said, 'A less melodramatic reason is that I would like to have the two of you who are innocent help me find the missing film of Villiers' paper.'

'Do you think it's there?' asked Ryger challengingly.

'Possibly. It's a beginning. We can then search each of your rooms. The symposium on Astronautics doesn't start till tomorrow at 10 a.m. We have till then.'

'And after that?'

'It may have to be the police.'

They stepped gingerly into Villiers' room. Ryger was red, Kaunas pale. Talliaferro tried to remain calm.

Last night they had seen it under artificial lighting with a scowling, disheveled Villiers clutching his pillow, staring them down, ordering them away. Now there was the scentless odor of death about it.

Mandel fiddled with the window polarizer to let more light in and adjusted it too far, so that the eastern

Sun slipped in.

Kaunas threw his arm up to shade his eyes and screamed, The Sun!' so that all the others froze.

Kaunas' face had gone into a kind of terror, as though it were his Mercurian Sun that he had caught a blinding glimpse of.

Talliaferro thought of his own reaction to the possibility of open air and his teeth gritted. They were all bent crooked by their ten years away from Earth.

Kaunas ran to the window, fumbling for the polarizer, and then the breath came out of him in a huge gasp.

Mandel stepped to his side. 'What's wrong?' and the other two joined them.

The city lay stretched below them and outward to the horizon in broken stone and brick, bathed in the rising Sun, with the shadowed portions toward them. Talliaferro cast it all a furtive and uneasy glance.

Kaunas, his chest seemingly contracted past the point where he could cry out, stared at something much closer. There, on the outer window sill, one corner secured hi a trifling imperfection, a crack in the cement, was an inch-long strip of milky-gray film, and on it were the early rays of the rising Sun.

Mandel, with an angry, incoherent cry, threw up the window and snatchedit away. He shielded it in one cupped hand, staring out of hot and reddened eyes.

He said, 'Wait here!'

There was nothing to say. When Mandel left, they sat down and stared stupidly at one another.

Mandel was back in twenty minutes. He said quietly-in a voice that gave the impression, somehow, that it was quiet only because its owner had passed far beyond the raving stage-The corner in the crack wasn't overexposed. I could make out a few words. It is Villiers' paper. The rest is ruined; nothing can be salvaged. It's gone.'

'What next?' said Talliaferro.

Mandel shrugged wearily. 'Right now, I don't care. Mass transference is gone until someone as brilliant as Villiers works it out again. I shall work on it, but I have no illusions as to my own capacity. With it gone, I suppose you three don't matter, guilty or not. What's the difference?' His whole body seemed to have loosened and sunk into despair.

But Talliaferro's voice grew hard. 'Now, hold on. In your eyes, any of the three of us might be guilty. I, for instance. You are a big man in the field and you will never have a good word to say for me. The general idea may arise that I am incompetent or worse. I will not be ruined by the shadow of guilt. Now let's solve this thing.'

'I am no detective,' said Mandel wearily.

Then why don't you call in the police, damn it?'

Ryger said, 'Wait awhile, Tal. Are you implying that I'm guilty?'

'I'm only saying that I'm innocent.'

Kaunas raised his voice in fright. 'It will mean the psychoprobe for each of us. There may be mental damage-'

Mandel raised both arms high in the air. 'Gentlemen! Gentlemen! Please! There is one thing we might do short of the police; and you are right, Dr. Talliaferro, it would be unfair to the innocent to leave this matter here.'

They turned to him in various stages of hostility. Ryger said, 'What do you suggest?'

'I have a friend named Wendell Urth. You may have heard of him, or you may not, but perhaps I can arrange to see him tonight.'

'What if we can?' demanded Talliaferro. 'Where does that get us?'

'He's an odd man,' said Mandel hesitantly. 'Very odd. And very brilliant in his way. He has helped the police before this and he may be able to help us now.'

Edward Talliaferro could not forbear staring at the room and its occupant with the greatest astonishment.

It and he seemed to exist in isolation, and to be part of no recognizable world. The sounds of Earth were absent in this well-padded, windowless nest. The light and air of Earth had been blanked out in artificial illumination and conditioning.

It was a large room, dim and cluttered. They had picked their way across a littered floor to a couch from which book-films had been brusquely cleared and dumped to one side in an amorphous tangle.

The man who owned the room had a large round face on a stumpy round body. He moved quickly about on his short legs, jerking his head as he spoke until his thick glasses all but bounced off the thoroughly inconspicuous nubbin that served in the office of a nose. His thick-lidded, somewhat protuberant eyes gleamed in myopic good nature at them all, as he seated himself in his own chair-desk combination, lit directly by the one bright light in the room.

'So good of you to come, gentlemen. Pray excuse the condition of my room.' He waved stubby fingers in a wide-sweeping gesture. 'I am engaged in cataloguing the many objects of extraterrological interest I have accumulated. It is a tremendous job. For instance-'

He dodged out of his seat and burrowed in a heap of objects beside the desk till he came up with a smoky gray object, semi-translucent and roughly cylindrical. 'This,' he said, 'is a Callistan object that may be a relic of intelligent nonhuman entities. It is not decided. No more than a dozen have been discovered and that is the most perfect single specimen I know of.'

He tossed it to one side and Talliaferro jumped. The plump man stared in his direction and said, 'It's not breakable.' He sat down again, clasped his pudgy fingers tightly over his abdomen and let them pump slowly in and out as he breathed. 'And now what can I do for you?'

Hubert Mandel had carried through the introductions and Talliaferro was considering deeply. Surely it was a man named Wendell Urth who had written a recent book entitled Comparative Evolutionary Processes on Water-Oxygen Planets, and surely this could not be the man.

He said, 'Are you the author of Comparative Evolutionary Processes, Dr. Urth?'

A beatific smile spread across Urth's face. 'You've read it?'

'Well, no, I haven't, but-'

Urth's expression grew instantly censorious. Then you should. Right now. Here, I have a copy.'

He bounced out of his chair again and Mandel cried, 'Now wait, Urth, first things first. This is serious.'

He virtually forced Urth back into his chair and began speaking rapidly as though to prevent any further side issues from erupting. He told the whole story with admirable word economy.

Urth reddened slowly as he listened. He seized his glasses and shoved them higher up on his nose. 'Mass transference!' he cried.

'I saw it with my own eyes,' said Mandel.

'And you never told me.'

'I was sworn to secrecy. The man was... peculiar. I explained that.'

Urth pounded the desk. 'How could you allow such a discovery to remain the property of an eccentric, Mandel? The knowledge should have been forced from him by psychoprobe, if necessary.'

'It would have killed him,' protested Mandel.

But Urth was rocking back and forth with his hands clasped tightly to his cheeks. 'Mass transference.

The only way a decent, civilized man could travel. The only possible way. The only conceivable way. If I had known. If I could have been there. But the hotel is nearly thirty miles away.'

Ryger, who listened with an expression of annoyance on his face, interposed, 'I understand there's a flitter line direct to Convention Hall. It could have got you there in ten minutes.'

Urth stiffened and looked at Ryger strangely. His cheeks bulged. He jumped to his feet and scurried out of the room.

Ryger said, 'What the devil?'

Mandel muttered, 'Damn it, I should have warned you.'

'About what?'

'Dr. Urth doesn't travel on any sort of conveyance. It's a phobia. He moves about only on foot.'

Kaunas blinked about in the dimness. 'But he's an extraterrologist, isn't he? An expert on life forms of other planets?'

Talliaferro had risen and now stood before a Galactic Lens on a pedestal. He stared at the inner gleam of the star systems. He had never seen a Lens so large or so elaborate.

Mandel said, 'He's an extraterrologist, yes, but he's never visited any of the planets on which he is expert and he never will. In thirty years, he's never been more than a few miles from this room.'

Ryger laughed.

Mandel flushed angrily. 'You may find it funny, but I'd appreciate your being careful what you say when Dr. Urth comes back.'

Urth sidled in a moment later. 'My apologies, gentlemen,' he said in a whisper. 'And now let us approach our problem. Perhaps one of you wishes to confess?'

Talliaferro's lips quirked sourly. This plump, self-imprisoned extraterrologist was scarcely formidable enough to force a confession from anyone. Fortunately there would be no need of him.

Talliaferro said, 'Dr. Urth, are you connected with the police?'

A certain smugness seemed to suffuse Urth's ruddy face. 'I have no official connection, Dr. Talliaferro, but my unofficial relationships are very good indeed.'

'In that case, I will give you some information which you can carry to the police.'

Urth drew in his abdomen and hitched at his shirttail. It came free and slowly he polished his glasses with it. When he was quite through and had perched them precariously on his nose once more, he said, 'And what is that?'

'I will tell you who was present when Villiers died and who scanned his paper.'

'You have solved the mystery?'

'I've thought about it all day. I think I've solved it.' Talliaferro rather enjoyed the sensation he was creating.

'Well, then?'

Talliaferro took a deep breath. This was not going to be easy to do, though he had been planning it for hours. The guilty man,' he said, 'is obviously Dr. Hubert Mandel.'

Mandel stared at Talliaferro in sudden, hard-breathing indignation. 'Look here, Doctor,' he began loudly, 'if you have any basis-'

Urth's tenor voice soared above the interruption. 'Let him talk, Hubert, let us hear him. You suspected him and there is no law that forbids him to suspect you.'

Mandel fell angrily silent.

Talliaferro, not allowing his voice to falter, said, 'It is more than just suspicion. Dr. Urth. The evidence is perfectly plain. Four of us knew about mass transference, but only one of us. Dr. Mandel, had actually seen a demonstration. He knew it to be a fact. He knew a paper on the subject existed. We three knew only that Villiers was more or less unbalanced. Oh, we might have thought there was just a chance. We visited him at eleven, I think, just to check on that, though none of us actually said so, but he only acted crazier than ever.

'Check special knowledge and motive then on Dr. Mandel's side. Now, Dr. Urth, picture something else. Whoever it was who confronted Villiers at midnight, saw him collapse, and scanned his paper (let's keep him anonymous for a moment) must have been terribly startled to see Villiers apparently come to life again and to hear him talking into the telephone. Our criminal, in the panic of the moment, realized one thing: he must get rid of the one piece of incriminating material evidence.

'He had to get rid of the undeveloped film of the paper and he had to do it in such a way that it would be safe from discovery so that he might pick it up once more if he remained unsuspected. The outer window sill was ideal. Quickly he threw up Villiers' window, placed the strip of film outside, and left. Now, even if

Villiers survived or if his telephoning brought results, it would be merely Villiers' word against his own and it would be easy to show that Villiers was unbalanced.'

Talliaferro paused in something like triumph. This would be irrefutable.

Wendell Urth blinked at him and wiggled the thumbs of his clasped hands so that they slapped against his ample shirt front. He said, 'And the significance of all that?'

The significance is that the window was thrown open and the film placed in open air. Now Ryger has lived for ten years on Ceres, Kaunas on Mercury, I on the Moon-barring short leaves and not many of them. We commented to one another several times yesterday on the difficulty of growing acclimated to Earth.

'Our work worlds are each airless objects. We never go out in the open without a suit. To expose ourselves to unenclosed space is unthinkable. None of us could have opened the window without a severe inner struggle. Dr. Mandel, however, has lived on Earth exclusively. Opening a window to him is only a matter of a bit of muscular exertion. He could do it. We couldn't. Ergo, he did it.'

Talliaferro sat back and smiled a bit.

'Space, that's it!' cried Ryger with enthusiasm.

That's not it at all,' roared Mandel, half-rising as though tempted to throw himself at Talliaferro. 'I deny the whole miserable fabrication. What about the record I have of Villiers' phone call? He used the word classmate. The entire tape makes it obvious-'

'He was a dying man,' said Talliaferro. 'Much of what he said you admitted was incomprehensible. I ask you, Dr. Mandel, without having heard the tape, if it isn't true that Villiers' voice is distorted past recognition?'

'Well-' said Mandel confused.

'I'm sure it is. There is no reason to suppose, then, that you might not have rigged up the tape in advance, complete with the damning word classmate.' Mandel said, 'Good lord, how would I know there were classmates at the Convention? How would I know they knew about the mass tranference?'

'Villiers might have told you. I presume he did.'

'Now, look,' said Mandel, 'you three saw Villiers alive at eleven. The medical examiner, seeing Villiers' body shortly after 3 a.m., declared he had been dead at least two hours. That was certain. The time of death therefore, was between ii p.m. and i a.m. I was at a late conference last night. I can prove my whereabouts, miles from the hotel, between ten and two, by a dozen witnesses, no one of whom anyone can possibly question. Is that enough for you?'

Talliaferro paused a moment. Then he went on stubbornly, 'Even so. Suppose you got back to the hotel by two-thirty. You went to Villiers' room to discuss his talk. You found the door open, or you had a duplicate key. Anyway, you found him dead. You seized the opportunity to scan the paper-'

'And if he were already dead, and couldn't make phone calls, why should I hide the film?'

To remove suspicion. You may have a second copy of the film safe in your possession. For that matter, we have only your own word that the paper itself was destroyed.'

'Enough. Enough!' cried Urth. 'It is an interesting hypothesis. Dr. Talliaferro, but it falls to the ground of its own weight.'

Talliaferro frowned. That's your opinion, perhaps-'

'It would be anyone's opinion. Anyone, that is, with the power of human thought. Don't you see that Hubert Mandel did too much to be the criminal?'

'No,' said Talliaferro.

Wendell Urth smiled benignly. 'As a scientist. Dr. Talliaferro, you undoubtedly know better than to fall in love with your own theories to the exclusion of facts or reasoning. Do me the pleasure of behaving similarly as a detective.

'Consider that if Dr. Mandel had brought about the death of Villiers and faked an alibi, or if he had found Villiers dead and taken advantage of that, how little he would really have had to do! Why scan the paper or even pretend that anyone had done so. He could simply have taken the paper. Who else knew of its existence? Nobody, really. There was no reason to think Villiers told anyone else about it. Villiers was pathologically secretive. There would have been every reason to think that he told no one.

'No one knew Villiers was giving a talk, except Dr. Man-del. It wasn't announced. No abstract was published. Dr. Mandel could have walked off with the paper in perfect confidence.

'Even if he had discovered that Villiers had talked to his classmates about the matter, what of it? What evidence would his classmates have except the word of one whom they are themselves willing to consider a madman?

'By announcing instead that Villiers' paper had been destroyed, by declaring his death to be not entirely natural, by searching for a scanned copy of the film-in short by everything Dr. Mandel has done, he has aroused a suspicion that only he could possibly have aroused when he need only have remained quiet to have committed a perfect crime. If he were the criminal, he would be more stupid, more colossally obtuse than anyone I have ever known. And Dr. Mandel, after all, is none of that.' Talliaferro thought hard but found nothing to say.

Ryger said, Then who did it?'

'One of you three. That's obvious.'

'But which?'

'Oh, that's obvious too. I knew which of you was guilty the moment Dr. Mandel had completed his description of events.'

Talliaferro stared at the plump extraterrologist with distaste. The bluff did not frighten him, but it was affecting the other two. Ryger's lips were thrust out and Kaunas' lower jaw had relaxed moronically. They looked like fish, both of them.

He said, 'Which one, then? Tell us.'

Urth blinked. 'First, I want to make it perfectly plain that the important thing is mass transference. It can still be recovered.'

Mandel, scowling still, said querulously, 'What the devil are you talking about, Urth?'

The man who scanned the paper probably looked at what he was scanning. I doubt that he had the time or the presence of mind to read it, and if he did, I doubt if he could remember it... consciously.

However, there is the psycho-probe. If he so much as glanced at the paper, what impinged on his retina could be probed.'

There was an uneasy stir.

Urth said at once, 'No need to be afraid of the psycho-probe. Proper handling is safe, particularly if a man offers himself voluntarily. When damage is done, it is usually because of unnecessary resistance, a kind of mental tearing, you know. So if the guilty man will voluntarily confess, place himself in my hands-'

Talliaferro laughed. The sudden noise rang out sharply in the dim quiet of the room. The psychology was so transparent and artless.

Wendell Urth looked almost bewildered at the reaction and stared earnestly at Talliaferro over his glasses. He said, 'I have enough influence with the police to keep the probing, entirely confidential.'

Ryger said savagely, 'I didn't do it.' Kaunas shook his head.

Talliaferro disdained any answer.

Urth sighed. 'Then I shall have to point out the guilty man. It will be traumatic. It will make things harder.'

He tightened the grip on his belly and his fingers twitched. 'Dr. Talliaferro indicated that the film was hidden on the outer window sill so that it might remain safe from discovery and from harm. I agree with him.'

'Thank you,' said Talliaferro dryly.

'However, why should anyone think that an outer window sill is a particularly safe hiding place? The police would certainly look there.

'Even in the absence of the police it was discovered. Who would tend to consider anything outside a building as particularly safe? Obviously some person who has lived a long time on an airless world has had it drilled into him that no one goes outside an enclosed place without detailed precautions.

To someone on the Moon, for instance, anything hidden outside a Lunar Dome would be comparatively safe. Men venture out only rarely and then only on specific business. So he would overcome the hardship of opening a window and exposing himself to what he would subconsciously consider a vacuum for the sake of a safe hiding place. The reflex thought, Outside an inhabited structure is safe, would do the trick.'

Talliaferro said between clenched teeth, 'Why do you mention the Moon, Dr. Urth?'

Urth said blandly, 'Only as an example. What I've said so far applies to all three of you. But now comes the crucial point, the matter of the dying night.'

Talliaferro frowned. 'You mean the night Villiers died?'

'I mean any night. See here, even granted that an outer window sill was a safe hiding place, which of you would be mad enough to consider it a safe hiding place for a piece of unexposed film? Scanner film isn't very sensitive, to be sure, and is made to be developed under all sorts of hit-and-miss conditions.

Diffuse nighttime illumination wouldn't seriously affect it, but diffuse daylight would ruin it in a few minutes, and direct sunlight would ruin it at once. Everyone knows that.'

Mandel said, 'Go ahead, Urth. What is this leading to?'

'You're trying to rush me,' said Urth, with a massive pout. 'I want you to see this clearly. The criminal wanted, above all, to keep the film safe. It was his only record of something of supreme value to himself and to the world. Why would he put it where it would inevitably be ruined almost immediately by the morning Sun? Only because he did not expect the morning Sun ever to come. He thought the night, so to speak, was immortal.

'But nights aren't immortal. On Earth they die and give way to daytime. Even the six-month polar night is a dying night eventually. The nights on Ceres last only two hours; the nights on the Moon last two weeks. They are dying nights too, and Drs. Talliaferro and Ryger know that day must always come.'

Kaunas rose. 'But wait-'

Wendell Urth faced him full. 'No longer any need to wait, Dr. Kaunas. Mercury is the only sizable object in the Solar System that turns only one face to the Sun. Even taking libration into account, fully three-eights of its surface is true dark-side and never sees the Sun. The Polar Observatory is at the rim of that dark-side. For ten years you have grown used to the fact that nights are immortal, that a surface in darkness remains eternally in darkness, and so you entrusted unexposed film to Earth's night, forgetting in your excitement that nights must die-'

Kaunas came forward. 'Wait-'

Urth was inexorable. 'I am told that when Mandel adjusted the polarizer in Villiers' room, you screamed at the sunlight. Was that your ingrained fear of the Mercurian Sun, or your sudden realization of what sunlight meant to your plans? You rushed forward. Was that to adjust the polarizer, or to stare at the ruined film?'

Kaunas fell to his knees. 'I didn't mean it. I wanted to speak to him, only to speak to him, and he screamed and collapsed. I thought he was dead and the paper was under his pillow and it all just followed. One thing led on to another and before I knew it I couldn't get out of it anymore. But I meant none of it. I swear it.'

They had formed a semicircle about him and Wendell Urth stared at the moaning Kaunas with pity in his eyes.

An ambulance had come and gone. Talliaferro finally brought himself to say stiffly to Mandel, 'I hope, sir, there will be no hard feelings for anything said here.'

And Mandel had answered as stiffly, 'I think we had all better forget as much as possible of what has happened during the last twenty-four hours.'

They were standing in the doorway, ready to leave, and Wendell Urth ducked his smiling head and said,

'There's the question of my fee, you know.' Mandell looked at him with a startled expression.

'Not money,' said Urth at once. 'But when the first mass transference setup for humans is established, I want a trip arranged for me right away.'

Mandel continued to look anxious. 'Now, wait. Trips through outer space are a long way off.'

Urth shook his head rapidly. 'Not outer space. Not at all. I would like to step across to Lower Falls, New Hampshire.'

'All right. But why?'

Urth looked up. To Talliaferro's outright surprise, the extraterrologist's face wore an expression compounded equally of shyness and eagerness.

Urth said, 'I once-quite a long time ago-knew a girl there. It's been many years-but I sometimes wonder...'

***

Some readers may realize that this story, first published in 1956, has been overtaken by events. In 1965, astronomers discovered that Mercury does not keep one side always to the Sun, but has a period of rotation of about fifty-four days, so that all parts of it are exposed to sunlight at one time or another. Well, what can I do except say that I wish astronomers would get things right to begin with? And I certainly refuse to change the story to suit their whims.

This item is not strictly a mystery in the usual sense of the word, or even a story in the usual sense of the word. I don't know how to describe it, except perhaps as a good-natured satire on scientific research. I received more mail alter its publication than alter any other item of comparable length. A particularly pleasant memory is that of receiving a telephone call from a man who spoke with a strong Central European accent. He said be was in Boston for a convention and wanted to thank me lor the pleasure 'Pate de Foie Gras' had given him, since it so amusingly and effectively poked knowledgeable fun at science. I tried to get his name, but he wouldn't give it to me. He was afraid, I suspect, that his reputation might suffer if it were found he read science fiction. If he is secretly reading this book and recognizes himself, I would like to assure him that he has plenty of company and can take off that plain wrapper. Honest!