n 1914, it was enemy aliens.

In 1930, it was Wobblies.

In 1957, it was fellow travelers.

And, in 1971....

"They could be anywhere," Andrew J. Burris said, with an expression which bordered on exasperated horror. "They could be all around us. Heaven only knows."

He pushed his chair back from his desk and stood up—a chunky little man with bright blue eyes and large hands. He paced to the window and looked out at Washington, and then he came back to the desk. A persistent office rumor held that he had become head of the FBI purely because he happened to have an initial J in his name, but in his case the J stood for Jeremiah. And, at the moment, his tone expressed all the hopelessness of that Old Testament prophet's lamentations.

"We're helpless," he said, looking at the young man with the crisp brown hair who was sitting across the desk. "That's what it is, we're helpless."

Kenneth Malone tried to look dependable. "Just tell me what to do," he said.

"You're a good agent, Kenneth," Burris said. "You're one of the best. That's why you've been picked for this job. And I want to say that I picked you personally. Believe me, there's never been anything like it before."

"I'll do my best," Malone said at random. He was twenty-eight, and he had been an FBI agent for three years. In that time, he had, among other things, managed to break up a gang of smugglers, track down a counterfeiting ring, and capture three kidnapers. For reasons which he could neither understand nor explain, no one seemed willing to attribute his record to luck.

"I know you will," Burris said. "And if anybody can crack this case, Malone, you're the man. It's just that—everything sounds so impossible. Even after all the conferences we've had."

"Conferences?" Malone said vaguely. He wished the chief would get to the point. Any point. He smiled gently across the desk and tried to look competent and dependable and reassuring. Burris' expression didn't change.

"You'll get the conference tapes later," Burris said. "You can study them before you leave. I suggest you study them very carefully, Malone. Don't be like me. Don't get confused." He buried his face in his hands. Malone waited patiently. After a few seconds, Burris looked up. "Did you read books when you were a child?" he asked.

Malone said: "What?"

"Books," Burris said. "When you were a child. Read them."

"Sure I did," Malone said. "'Bomba the Jungle Boy,' and 'Doolittle,' and 'Lucky Starr,' and 'Little Women'—"

"'Little Women'?"

"When Beth died," Malone said, "I wanted to cry. But I didn't. My father said big boys don't cry."

"And your father was right," Burris said. "Why, when I was a ... never mind. Forget about Beth and your father. Think about 'Lucky Starr' for a minute. Remember him?"

"Sure," Malone said. "I liked those books. You know, it's funny, but the books you read when you're a kid, they kind of stay with you. Know what I mean? I can still remember that one about Venus, for instance. Gee, that was—"

"Never mind about Venus, too," Burris said sharply. "Keep your mind on the problem."

"Yes, sir," Malone said. He paused. "What problem, sir?" he added.

"The problem we're discussing," Burris said. He gave Malone a bright, blank stare. "Just listen to me."

"Yes, sir."

"All right, then." Burris took a deep breath. He seemed nervous. Once again he stood up and went to the window. This time, he spoke without turning. "Remember how everybody used to laugh about spaceships, and orbital satellites, and life on other planets? That was just in those 'Lucky Starr' books. That was all just for kids, wasn't it?"

"Well, I don't know," Malone said slowly.

"Sure it was all for kids," Burris said. "It was laughable. Nobody took it seriously."

"Well, somebody must—"

"You just keep quiet and listen," Burris said.

"Yes, sir," Malone said.

Burris nodded. His hands were clasped behind his back. "We're not laughing any more, are we, Malone?" he said without moving.

There was silence.

"Well, are we?"

"Did you want me to answer, sir?"

"Of course I did!" Burris snapped.

"You told me to keep quiet and—"

"Never mind what I told you," Burris said. "Just do what I told you."

"Yes, sir," Malone said. "No, sir," he added after a second.

"No, sir, what?" Burris asked softly.

"No, sir, we're not laughing any more," Malone said.

"Ah," Burris said. "And why aren't we laughing any more?"

There was a little pause. Malone said, tentatively: "Because there's nothing to laugh about, sir?"

Burris whirled. "On the head!" he said happily. "You've hit the nail on the head, Kenneth. I knew I could depend on you." His voice grew serious again, and thoughtful. "We're not laughing any more because there's nothing to laugh about. We have orbital satellites, and we've landed on the Moon with an atomic rocket. The planets are the next step, and after that the stars. Man's heritage, Kenneth. The stars. And the stars, Kenneth, belong to Man—not to the Soviets!"

"Yes, sir," Malone said soberly.

"So," Burris said, "we should learn not to laugh any more. But have we?"

"I don't know, sir."

"We haven't," Burris said with decision. "Can you read my mind?"

"No, sir," Malone said.

"Can I read your mind?"

Malone hesitated. At last he said: "Not that I know of, sir."

"Well, I can't," Burris snapped. "And can any of us read each other's mind?"

Malone shook his head. "No, sir," he said.

Burris nodded. "That's the problem," he said. "That's the case I'm sending you out to crack."

This time, the silence was a long one.

At last, Malone said: "What problem, sir?"

"Mind reading," Burris said. "There's a spy at work in the Nevada plant, Kenneth. And the spy is a telepath."

---

The video tapes were very clear and very complete. There were a great many of them, and it was long after nine o'clock when Kenneth Malone decided to take a break and get some fresh air. Washington was a good city for walking, even at night, and Malone liked to walk. Sometimes he pretended, even to himself, that he got his best ideas while walking, but he knew perfectly well that wasn't true. His best ideas just seemed to come to him, out of nowhere, precisely as the situation demanded them.

He was just lucky, that was all. He had a talent for being lucky. But nobody would ever believe that. A record like his was spectacular, even in the annals of the FBI, and Burris himself believed that the record showed some kind of superior ability.

Malone knew that wasn't true, but what could he do about it? After all, he didn't want to resign, did he? It was kind of romantic and exciting to be an FBI agent, even after three years. A man got a chance to travel around a lot and see things, and it was interesting. The pay was pretty good, too.

The only trouble was that, if he didn't quit, he was going to have to find a telepath.

The notion of telepathic spies just didn't sound right to Malone. It bothered him in a remote sort of way. Not that the idea of telepathy itself was alien to him—after all, he was even more aware than the average citizen that research had been going on in that field for something over a quarter of a century, and that the research was even speeding up.

But the cold fact that a telepathy-detecting device had been invented somehow shocked his sense of propriety, and his notions of privacy. It wasn't decent, that was all.

There ought to be something sacred, he told himself angrily.

He stopped walking and looked up. He was on Pennsylvania Avenue, heading toward the White House.

That was no good. He went to the corner and turned off, down the block. He had, he told himself, nothing at all to see the President about.

Not yet, anyhow.

The streets were dark and very peaceful. I get my best ideas while walking, Malone said without convincing himself. He thought back to the video tapes.

The report on the original use of the machine itself had been on one of the first tapes, and Malone could still see and hear it. That was one thing he did have, he reflected; his memory was pretty good.

Burris had been the first speaker on the tapes, and he'd given the serial and reference number in a cold, matter-of-fact voice. His face had been perfectly blank, and he looked just like the head of the FBI people were accustomed to seeing on their TV and newsreel screens. Malone wondered what had happened to him between the time the tapes had been made and the time he'd sent for Malone.

Maybe the whole notion of telepathy was beginning to get him, Malone thought.

Burris recited the standard tape opening in a rapid mumble: "Any person or agent unauthorized for this tape please refrain from viewing further, under penalties as prescribed by law." Then he looked off, out past the screen to the left, and said: "Dr. Thomas O'Connor, of Westinghouse Laboratories. Will you come here, Dr. O'Connor?"

Dr. O'Connor came into the lighted square of screen slowly, looking all around him. "This is very fascinating," he said, blinking in the lamplight. "I hadn't realized that you people took so many precautions—"

He was, Malone thought, somewhere between fifty and sixty, tall and thin with skin so transparent that he nearly looked like a living X ray. He had pale blue eyes and pale white hair and, Malone thought, if there ever were a contest for the best-looking ghost, Dr. Thomas O'Connor would win it hands—or phalanges—down.

"This is all necessary for the national security," Burris said, a little sternly.

"Oh," Dr. O'Connor said quickly, "I realize that, of course. Naturally. I can certainly see that."

"Let's go ahead, shall we?" Burris said.

O'Connor nodded. "Certainly. Certainly."

Burris said: "Well, then," and paused. After a second he started again: "Now, Dr. O'Connor, would you please give us a sort of verbal run-down on this for our records?"

"Of course," Dr. O'Connor said. He smiled into the video cameras and cleared his throat. "I take it you don't want an explanation of how this machine works. I mean: you don't want a technical exposition, do you?"

"No," Burris said, and added: "Not by any means. Just tell us what it does."

---

Dr. O'Connor suddenly reminded Malone of a professor he'd had in college for one of the law courses. He had, Malone thought, the same smiling gravity of demeanor, the same condescending attitude of absolute authority. It was clear that Dr. O'Connor lived in a world of his own, a world that was not even touched by the common run of men.

"Well," he began, "to put it very simply, the device indicates whether or not a man's mental ... ah ... processes are being influenced by outside ... by outside influences." He gave the cameras another little smile. "If you will allow me, I will demonstrate on the machine itself."

He took two steps that carried him out of camera range, and returned wheeling a large heavy-looking box. Dangling from the metal covering were a number of wires and attachments. A long cord led from the box to the floor, and snaked out of sight to the left.

"Now," Dr. O'Connor said. He selected a single lead, apparently, Malone thought, at random. "This electrode—"

"Just a moment, doctor," Burris said. He was eying the machine with a combination of suspicion and awe. "A while back you mentioned something about 'outside influences.' Just what, specifically, does that mean?"

With some regret, Dr. O'Connor dropped the lead. "Telepathy," he said. "By outside influences, I meant influences on the mind, such as telepathy or mind reading of some nature."

"I see," Burris said. "You can detect a telepath with this machine."

"I'm afraid—"

"Well, some kind of a mind reader anyhow," Burris said. "We won't quarrel about terms."

"Certainly not," Dr. O'Connor said. The smile he turned on Burris was as cold and empty as the inside of Orbital Station One. "What I meant was ... if you will permit me to continue ... that we cannot detect any sort of telepath or mind reader with this device. To be frank, I very much wish that we could; it would make everything a great deal simpler. However, the laws of psionics don't seem to operate that way."

"Well, then," Burris said, "what does the thing do?" His face wore a mask of confusion. Momentarily, Malone felt sorry for his chief. He could remember how he'd felt, himself, when that law professor had come up with a particularly baffling question in class.

"This machine," Dr. O'Connor said with authority, "detects the slight variations in mental activity that occur when a person's mind is being read."

"You mean, if my mind were being read right now—"

"Not right now," Dr. O'Connor said. "You see, the bulk of this machine is in Nevada; the structure is both too heavy and too delicate for transport. And there are other qualifications—"

"I meant theoretically," Burris said.

"Theoretically," Dr. O'Connor began, and smiled again, "if your mind were being read, this machine would detect it, supposing that the machine were in operating condition and all of the other qualifications had been met. You see, Mr. Burris, no matter how poor a telepath a man may be, he has some slight ability—even if only very slight—to detect the fact that his mind is being read."

"You mean, if somebody were reading my mind, I'd know it?" Burris said. His face showed, Malone realized, that he plainly disbelieved this statement.

"You would know it," Dr. O'Connor said, "but you would never know you knew it. To elucidate: in a normal person—like you, for instance, or even like myself—the state of having one's mind read merely results in a vague, almost subconscious feeling of irritation, something that could easily be attributed to minor worries, or fluctuations in one's hormonal balance. The hormonal balance, Mr. Burris, is—"

"Thank you," Burris said with a trace of irritation. "I know what hormones are."

"Ah. Good," Dr. O'Connor said equably. "In any case, to continue: this machine interprets those specific feelings as indications that the mind is being ... ah ... 'eavesdropped' upon."

You could almost see the quotation marks around what Dr. O'Connor considered slang dropping into place, Malone thought.

---

"I see," Burris said with a disappointed air. "But what do you mean, it won't detect a telepath? Have you ever actually worked with a telepath?"

"Certainly we have," Dr. O'Connor said. "If we hadn't, how would we be able to tell that the machine was, in fact, indicating the presence of telepathy? The theoretical state of the art is not, at present, sufficiently developed to enable us to—"

"I see," Burris said hurriedly. "Only wait a minute."

"Yes?"

"You mean you've actually got a real mind reader? You've found one? One that works?"

Dr. O'Connor shook his head sadly. "I'm afraid I should have said, Mr. Burris, that we did once have one," he admitted. "He was, unfortunately, an imbecile, with a mental age between five and six, as nearly as we were able to judge."

"An imbecile?" Burris said. "But how were you able to—"

"He could repeat a person's thoughts word for word," Dr. O'Connor said. "Of course, he was utterly incapable of understanding the meaning behind them. That didn't matter; he simply repeated whatever you were thinking. Rather disconcerting."

"I'm sure," Burris said. "But he was really an imbecile? There wasn't any chance of—"

"Of curing him?" Dr. O'Connor said. "None, I'm afraid. We did at one time feel that there had been a mental breakdown early in the boy's life, and, indeed, it's perfectly possible that he was normal for the first year or so. The records we did manage to get on that period, however, were very much confused, and there was never any way of telling anything at all, for certain. It's easy to see what caused the confusion, of course: telepathy in an imbecile is rather an oddity—and any normal adult would probably be rather hesitant about admitting that he was capable of it. That's why we have not found another subject; we must merely sit back and wait for lightning to strike."

Burris sighed. "I see your problem," he said. "But what happened to this imbecile boy of yours?"

"Very sad," Dr. O'Connor said. "Six months ago, at the age of fifteen, the boy simply died. He simply—gave up, and died."

"Gave up?"

"That was as good an explanation as our medical department was able to provide, Mr. Burris. There was some malfunction, but—we like to say that he simply gave up. Living became too difficult for him."

"All right," Burris said after a pause. "This telepath of yours is dead, and there aren't any more where he came from. Or if there are, you don't know how to look for them. All right. But to get back to this machine of yours: it couldn't detect the boy's ability?"

Dr. O'Connor shook his head. "No, I'm afraid not. We've worked hard on that problem at Westinghouse, Mr. Burris, but we haven't yet been able to find a method of actually detecting telepaths."

"But you can detect—"

"That's right," Dr. O'Connor said. "We can detect the fact that a man's mind is being read." He stopped, and his face became suddenly morose. When he spoke again, he sounded guilty, as if he were making an admission that pained him. "Of course, Mr. Burris, there's nothing we can do about a man's mind being read. Nothing whatever." He essayed a grin that didn't look very healthy. "But at least," he said, "you know you're being spied on."

Burris grimaced. There was a little silence while Dr. O'Connor stroked the metal box meditatively, as if it were the head of his beloved.

At last, Burris said: "Dr. O'Connor, how sure can you be of all this?"

The look he received made all the previous conversation seem as warm and friendly as a Christmas party by comparison. It was a look that froze the air of the room into a solid chunk, Malone thought, a chunk you could have chipped pieces from, for souvenirs, later, when Dr. O'Connor had gone and you could get into the room without any danger of being quick-frozen by the man's unfriendly eye.

"Mr. Burris," Dr. O'Connor said in a voice that matched the temperature of his gaze, "please. Remember our slogan."

---

Malone sighed. He fished in his pocket for a pack of cigarettes, found one, and extracted a single cigarette. He stuck it in his mouth and started fishing in various pockets for his lighter.

He sighed again. He preferred cigars, a habit he'd acquired from the days when he'd filched them from his father's cigar case, but his mental picture of the fearless and alert young FBI agent didn't include a cigar. Somehow, remembering his father as neither fearless nor, exactly, alert—anyway, not the way the movies and the TV screens liked to picture the words—he had the impression that cigars looked out of place on FBI agents.

And it was, in any case, a small sacrifice to make. He found his lighter and shielded it from the brisk wind. He looked out over water at the Jefferson Memorial, and was surprised that he'd managed to walk as far as he had. Then he stopped thinking about walking, and took a puff of his cigarette, and forced himself to think about the job in hand.

Naturally, the Westinghouse gadget had been declared Ultra Top Secret as soon as it had been worked out. Virtually everything was, these days. And the whole group involved in the machine and its workings had been transferred without delay to the United States Laboratories out in Yucca Flats, Nevada.

Out there in the desert, there just wasn't much to do, Malone supposed, except to play with the machine. And, of course, look at the scenery. But when you've seen one desert, Malone thought confusedly, you've seen them all.

So, the scientists ran experiments on the machine, and they made a discovery of a kind they hadn't been looking for.

Somebody, they discovered, was picking the brains of the scientists there.

Not the brains of the people working with the telepathy machine.

And not the brains of the people working on the several other Earth-limited projects at Yucca Flats.

They'd been reading the minds of some of the scientists working on the new and highly classified non-rocket space drive.

In other words, the Yucca Flats plant was infested with a telepathic spy. And how do you go about finding a telepath? Malone sighed. Spies that got information in any of the usual ways were tough enough to locate. A telepathic spy was a lot tougher proposition.

Well, one thing about Andrew J. Burris—he had an answer for everything. Malone thought of what his chief had said: "It takes a thief to catch a thief. And if the Westinghouse machine won't locate a telepathic spy, I know what will."

"What?" Malone had asked.

"It's simple," Burris had said. "Another telepath. There has to be one around somewhere. Westinghouse did have one, after all, and the Russians still have one. Malone, that's your job: go out and find me a telepath."

Burris had an answer for everything, all right, Malone thought. But he couldn't see where the answer did him very much good. After all, if it takes a telepath to catch a telepath, how do you catch the telepath you're going to use to catch the first telepath?