Earthlight (Arthur C. Clarke Collection)

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  ramp, Sadler could see that the building extended downward for an immense distance. A very long way below was something that looked like a large net. He did some mental calculations, then decided that it would, after all, be adequate to break the fall of anyone foolish enough to go over the edge. The architects of lunar buildings had a light-hearted approach to gravity which would lead to instant disaster on Earth.

  The upper concourse was exactly like the one by which they had entered, but there were fewer people about and one could tell that, however democratic the Autonomous Lunar Republic might be, there were subtle class distinctions here as in all other cultures that man had ever created. There was no more aristoc­racy of birth or wealth, but that of responsibility would always exist. Here, no doubt, lived the people who really ran the Moon. They had few more possessions, and a good many more worries, than their fellow citizens on the floors below, and there was a continual interchange from one level to another.

  Sadler's small guide led him out of this central concourse along yet another moving passageway, then finally into a quiet corridor with a narrow strip of garden down its center and a fountain playing at either end. He marched up to one of the doors and announced: "Here's place." The brusqueness of his statement was quite neutralized by the proud there-wasn't-that-clever-of-me smile he gave Sadler, who was now wondering what would be a suitable reward for his enterprise. Or would the boy be offended if he gave him anything?

  This social dilemma was solved for him by his observant guide.

  "More than ten floors, that's fifteen."

  So there's a standard rate, thought Sadler. He handed over a quarter, and to his surprise was compelled to accept the change. He had not realized that the well-known lunar virtues of hon­esty, enterprise and fair-dealing started at such an early age.

  "Don't go yet," he said to his guide as he rang the doorbell. "If there's no one in, I'll want you to take me back."

  "You not phoned first?" said that practical person, looking at him incredulously.

  Sadler felt it was useless to explain. The inefficiencies and vagaries of old-fashioned Earth-folk were not appreciated by

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  these energetic colonists—though heaven help him if he ever used that word here.

  However, there was no need for the precaution. The man he wanted to meet was at home, and Sadler's guide waved him a cheerful good-by as he went off down the corridor, whistling a tune that had just arrived from Mars.

  "I wonder if you remember me," said Sadler. "I was at the Plato Observatory during the Battle of Pico. My name's Ber­tram Sadler."

  "Sadler? Sadler? Sorry, but I don't remember you at the moment. But come right in; I'm always pleased to meet old friends."

  Sadler followed into the house, looking round curiously as he did so. It was the first time he had ever been into a private home on the Moon, and as he might have expected there was no way in which it could be distinguished from a similar resi­dence on Earth. That it was one cell in a vast honeycomb did not make it any less a home; it had been two centuries since more than a minute fraction of the human race had lived in separate, isolated buildings and the word "house" had changed its mean­ing with the times,

  There was just one touch in the main living room, however, that was too old-fashioned for any terrestrial family. Extend­ing halfway across one wall was a large animated mural of a kind which Sadler had not seen for years. It showed a snow-flecked mountainside sloping down to a tiny Alpine village a kilometer or more below. Despite the apparent distance, every detail was crystal clear; the little houses and the toy church had the sharp, vivid distinctness of something seen through the wrong end of a telescope. Beyond the village, the ground rose again, more and more steeply, to the great mountain that dominated the skyline and trailed from its summit a perpetual plume of snow, a white streamer drifting forever down the wind.

  It was, Sadler guessed, a real scene recorded a couple of cen­turies ago. But he could not be sure; Earth still had such sur­prises in out-of-the-way spots.

  He took the seat he was offered and had his first good look at the man he had played truant from rather important business to meet. "You don't remember me?" he said.

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  "I'm afraid not—but I'm quite bad at names and faces."

  "Well, I'm nearly twice as old now, so it's not surprising. But you haven't changed, Professor Molton. I can still remember that you were the first man I ever spoke to on my way to the Observatory. I was riding the monorail from Central City, watching the sun going down behind the Apennines. It was the night before the Battle of Pico, and my first visit to the Moon."

  Sadler could see that Molton was genuinely baffled. It was thirty years, after all, and he must not forget that he had a completely abnormal memory for faces and facts.

  "Never mind," he continued. "I couldn't really expect you to remember me, because I wasn't one of your colleagues. I was only a visitor to the Observatory, and I wasn't there long. I'm an accountant, not an astronomer."

  "Indeed?" said Molton, clearly still at a loss.

  "That was not, however, the capacity in which I visited the Observatory, though I pretended it was. At the time, I was actually a government agent investigating a security leak."

  He was watching the old man's face intently, and there was no mistaking the flicker of surprise. After a short silence, Mol­ton replied, "I seem to remember something of the kind. But I'd quite forgotten the name. It was such a long time ago, of course."

  "Yes, of course," echoed Sadler. "But I'm sure there are some things you'll remember. However, before I go on, there's one thing I'd better make clear. My visit here is quite unofficial. I really am nothing but an accountant now, and I'm glad to say quite a successful one. In fact, I'm one of the partners of Carter, Hargreaves and Tillotson, and I'm here to audit a number of the big lunar corporations. Your Chamber of Commerce will confirm that."

  "I don't quite see " began Molton.

  "—what it's all got to do with you? Well, let me jog your memory. I was sent to the Observatory to investigate a security leak. Somehow, information was getting to the Federation. One of our agents had reported that the leak was at the Observatory, and I went there to look for it."

  "Go on," said Molton.

  Sadler smiled, a little wryly.

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  "I'm considered to be a good accountant," he said, "but I'm afraid I was not a very successful security man. I suspected a lot of people, but found nothing, though I accidentally uncovered one crook."

  "Jenkins," said Molton suddenly.

  "That's right—your memory's not so bad, Professor. Anyway, I never found the spy; I couldn't even prove that he existed, though I investigated every possibility I could think of. The whole affair fizzled out eventually, of course, and a few months later I was back at my normal work, and much happier too. But it has always worried me; it was a loose end I didn't like having round—a discrepancy in the balance sheet. I'd given up any hope of settling it, until a couple of weeks ago. Then I read Commo­dore Brennan's book. Have you seen it yet?"

  "I'm afraid not, though of course I've heard about it."

  Sadler reached into his briefcase and produced a fat volume, which he handed over to Molton.

  "I've brought a copy for you—I know you'll be very inter­ested. It's quite a sensational book, as you can judge by the fuss it's causing all over the System. He doesn't pull any punches, and I can understand why a lot of people in the Federation are pretty mad with him. However, that's not the point that con­cerns me. What I found quite fascinating was his account of the events leading up to the Battle of Pico. Imagine my surprise when he definitely confirmed that vital information had come from the Observatory. To quote his phrase: 'One of Earth's leading astronomers, by a brilliant technical subterfuge, kept us informed of developments during the progress of Project Thor. It would be improper to give his name, but he is now living in honored retirement on the Moon.' "

  Ther
e was a very long pause. Molton's craggy face had now set in granite folds, and gave no hint of his emotions.

  "Professor Molton," Sadler continued earnestly. "I hope you'll believe me when I say that I'm here purely out of private curiosity. In any case, you're a citizen of the Republic—there's nothing I could do to you even if I wanted to. But I know you were that agent. The description fits, and I've ruled out all the other possibilities. Moreover, some friends of mine in the Fed­eration have been looking at records, again quite unofficially.

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  It's not the slightest use pretending you know nothing about it. If you don't want to talk, I'll clear out. But if you feel like telling me—and I don't see how it matters now—I'd give a very great deal to know how you managed to do it."

  Molton had opened Professor, late Commodore, Brennan's book and was leafing through the index. Then he shook his head in some annoyance.

  "He shouldn't have said that," he remarked testily, to no one in particular. Sadler breathed a sigh of satisfied anticipa­tion. Abruptly, the old scientist turned upon him.

  "If I tell you, what use will you make of the information?"

  "None, I swear."

  "Some of my colleagues might be annoyed, even after this time. It wasn't easy, you know. / didn't enjoy it either. But Earth had to be stopped, and I think I did the right thing."

  "Professor Jamieson—he's director now, isn't he?—had similar ideas. But he didn't put them into practice."

  "I know. There was a time when I nearly confided in him, but perhaps it's just as well that I didn't."

  Molton paused reflectively, and his face creased into a smile.

  "I've just remembered," he said. "I showed you round my lab. I was a little bit suspicious then—I thought it odd you should have come when you did. So I showed you absolutely everything, until I could see you were bored and had had enough."

  "That happened rather often," said Sadler dryly. "There was quite a lot of equipment at the Observatory."

  "Some of mine, however, was unique. Not even a man in my own field would have guessed what it did. I suppose your people were looking for concealed radio transmitters, and that sort of thing?"

  "Yes; we had monitors on the lookout, but they never spotted anything."

  Molton was obviously beginning to enjoy himself. Perhaps he too, thought Sadler, had been frustrated for the last thirty years, unable to say how he had fooled the security forces of Earth.

  "The beauty of it was," Molten continued, "my transmitter was in full sight all the time. In fact, it was about the most

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  obvious thing in the Observatory. You see, it was the thousand-centimeter telescope."

  Sadler stared at him incredulously.

  "I don't understand you."

  "Consider," said Molton, becoming once more the college professor he had been after leaving the Observatory, "exactly what it is a telescope does. It gathers light from a tiny portion of the sky, and brings it accurately to a focus on a photographic plate or the slit of a spectroscope. But don't you see—a tele­scope can work both ways."

  "I'm beginning to follow."

  "My observing program involved using the thousand centi­meter for studying faint stars. I worked in the far ultra-violet —which of course is quite invisible to the eye. I'd only to re­place my usual instruments by an ultra-violet lamp, and the telescope immediately became a searchlight of immense power and accuracy, sending out a beam so narrow that it could only be detected in the exact portion of the sky I'd aimed it at. Interrupting the beam for signaling purposes was, of course, a trivial problem. I can't send Morse, but I built an automa­tic modulator to do it for me."

  Sadler slowly absorbed this revelation. Once explained, the idea was ridiculously simple. Yes, any telescope, now he came to think of it, must be capable of working both ways—of gathering light from the stars, or of sending an almost per­fectly parallel beam back at them, if one shone a light into the eyepiece end. Molton had turned the thousand-centimeter reflector into the largest electric torch ever built.

  "Where did you aim your signals?" he asked.

  "The Federation had a small ship about ten million kilo­meters out. Even at that distance, my beam was still pretty narrow and it needed good navigation to keep in it. The ar­rangement was that the ship would always keep dead in line between me and a faint northern star that was always visible above my horizon. When I wanted to send a signal—they knew when I would be operating, of course—I merely had to feed the co-ordinates into the telescope, and I'd be sure that they'd receive me. They had a small telescope aboard, with an ultra-violet detector. They kept in contact with Mars by ordi-

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  nary radio. I often thought it must have been very dull out there, just listening for me. Sometimes I didn't send anything for days."

  "That's another point," Sadler remarked. "How did the in­formation get to you, anyway?"

  "Oh, there were two methods. We got copies of all the astronomical journals, of course. There were agreed pages in certain journals—The Observatory, I recall, was one of them— that I kept my eye on. Some of the letters were fluorescent under far ultra-violet. No one could have spotted it; ordinary u.v. was no use."

  "And the other method?"

  "I used to go to the gym in Central City every weekend. You leave your clothes in locked cubicles when you undress, but there's enough clearance at the top of the doors for any­thing to be slipped in. Sometimes I used to find an ordinary tabulating-machine card on top of my things, with a set of holes punched in it. Perfectly commonplace and innocent, of course—you'll find them all over the Observatory, and not only in the Computing section. I always made a point of having a few genuine ones in my pockets. When I got back, I'd deci­pher the card and send the message out on my next transmis­sion. I never knew what I was sending—it was always in code. And I never discovered who dropped the cards in my locker."

  Molton paused, and looked quizzically at Sadler.

  "On the whole," he concluded, "I really don't think you had much chance. My only danger was that you might catch my contacts and find they were passing information to me. Even if that happened, I thought I could get away with it. Every piece of apparatus I used had some perfectly genuine astronomi­cal function. Even the modulator was part of an unsuccessful spectrum analyzer I'd never bothered to dismantle. And my transmissions only lasted for a few minutes; I could send a lot in that time, and then get on with my regular program."

  Sadler looked at the old astronomer with undisguised ad­miration. He was beginning to feel a good deal better: an ancient inferiority complex had been exorcised. There was no need for self-reproach; he doubted if anyone could have de­tected Molton's activities, while they were confined to the

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  Observatory end alone. The people to blame were the counter-agents in Central City and Project Thor, who should have stopped the leak further up the line.

  There was still one question that Sadler wished to ask, but could not bring himself to do so; it was, after all, no real concern of his. How was no longer a mystery; why still re­mained.

  He could think of many answers. His studies of the past had shown him that a man like Molton would not become a spy for money, or power, or any such trivial reason. Some emotional impulse must have driven him on the path he followed, and he would have acted from a profound inner conviction that what he did was right. Logic might have told him that the Federation should be supported against Earth, but in a case like this, logic was never enough.

  Here was one secret that would remain with Molton. Per­haps he was aware of Sadler's thoughts, for abruptly he walked over to the wide bookcase and slid aside a section of the paneling.

  "I came across a quotation once," he said, "that's been a considerable comfort to me. I'm not sure whether it was sup­ posed to be cynical or not, but there's a great deal of truth in it. It was made, I believe, by a French statesman named Talleyrand, about four hundred years ago. And he said this:
'What is trea­ son? Merely a matter of dates.' You might care to think that over, Mr. Sadler."

  He walked back from the bookcase, carrying two glasses and a large decanter.

  "A hobby of mine," he informed Sadler. "The last vintage from Hesperus. The French make fun of it, but I'd match it against anything from Earth."

  They touched glasses.

  "To peace among the planets," said Professor Molton, "and may no men ever again have to play the parts we did."

  Against a landscape four hundred thousand kilometers away in space and two centuries ago in time, spy and counterspy drank the toast together. Each was full of memories, but those memories held no bitterness now. There was nothing more to say: for both of them, the story was ended.