Trail's end, Pluto's single community, cowering at the foot of a towering black mountain, seemed deserted. There was no stir of life about the buildings that huddled between the spacefield and the mountain. The spiraling tower of the radio station climbed dizzily spaceward and beside it squatted the tiny radio shack. Behind it stood the fueling station and the hangar, while half a mile away loomed the larger building that housed the laboratories of the Solar Science commission.

Caroline moved closer to Gary.

"It seems so lonely," she whispered. "I don't like loneliness now…

after…”

Gary stirred uneasily, scraping the heavy boots of his spacesuit over the pitted rock. "It's always lonely enough," he said. "I wonder where they are.”

As he spoke the lock of the radio shack opened and a space-suited figure strode across the field to meet them.

His voice crackled in their helmet phones. "You must be Nelson," it said.

"I'm Ted Smith, operator here. Kingsley told me to bring you up to the house right away.”

"Fine," said Gary. "Glad to be here. I suppose Evans is still around.”

"He is," said Smith. "He's up at the house now. His ship is in the hangar.

Personally, I figure he's planning to take off and let the SCC do what they can about it.”

Smith fell in step with them. "It's good to see new faces," he declared, "especially a woman. We don't have women visitors very often.”

"I'm sorry," said Gary. "I forgot.”

He introduced Caroline and Herb to Smith as they plodded past the radio shack and started for the laboratory.

"It gets God-lonesome out here," said Smith. "This is a hellish place, if I do say so myself. No wind. No moon. No nothing. Very little difference between day and night because there's never any clouds to cover the stars and even in the daytime the Sun is little better than a star.”

His tongue, loosened by visitors to talk to, rambled on. "A fellow gets kind of queer out here," he told them.

"It's enough to make anyone get queer. I think the doctor is half crazy from staying here too long. He thinks he's getting messages from some place far away. Acts mysterious about it.”

"You think he just imagines it?" asked Herb.

"I'm not saying one way or the other," declared Smith, "but I ask you…

where would you get the messages from? Think of the power it would take just to send a message from Alpha Centauri. And that isn't so very far away. Not so far as stars go. Right next door, you might say.”

"Evans is going to fly there and back," Herb reminded him.

"Evans is space-nuts," said Smith. "With all the solar system to fool around in, he has to go gallivanting off to the stars. He hasn't got a chance. I told him so, but he laughed at me. I'm sorry for him. He's a nice young fellow.”

They mounted the steps, hewn out of living stone, which led to the main airlock of the laboratory building. Smith pressed a button and they waited.

"I suppose you'll want Andy to go over your ship,”

Smith suggested.

"Sure," said Gary. "Tell him to take good care of it.”

"Andy is the fueling-station man," the radio operator explained. "But he hasn't much to do now. Most of the ships use geosectors. There's only a few old tubs, one or two a year, that need any fuel. Used to be a good business, but not any more.”

The space lock swung open and the three stepped inside. Smith remained by the doorway.

"I have to go back to the shack," he said. "I'll see you again before you leave.”

The lock hissed shut behind them and the inner screw began to turn. It swung open and they stepped into a small room that was lined with spacesuits hanging on the wall.

A man was standing in the center of the room. A big man, with broad shoulders and hands like hams. His unruly shock of hair was jet-black and his voice boomed jovially at them.

"Glad to see all of you," he said and laughed, a deep, thunderous laugh that seemed to shake the room.

Gary swung back the helmet of his suit and thrust out a gloved hand.

"You are Dr. Kingsley?" he asked.

"That's who I am," boomed the mighty voice. "And who are these folks with you?”

Gary introduced them.

"I didn't know there was a lady in the party," said the doctor.

"There wasn't," said Herb. "Not until just recently.”

"Mean to tell me they've taken to hitch-hiking out in space?”

Gary laughed. "Even better than that, doctor," he said. "There's a little story about Miss Martin you'll enjoy.”

"Come on," he roared at them. "Get out of your duds. I got some coffee brewing. And you'll want to meet Tommy Evans. He's that young fool who thinks he's going to fly four light-years out to old A.C.”

And at just that moment Tommy Evans burst into the room.

"Doc," he shouted, "that damn machine of yours is at it again.”

Dr. Kingsley turned and lumbered out, shouting back at them.

"Come along. Never mind the suits.”

They ran behind him as he lumbered along. Through what obviously were the laboratory's living quarters, through a tiny kitchen that smelled of boiling coffee, into a workroom bare of everything except a machine that stood in one corner. A red light atop the machine was blinking rapidly.

"Whatever you say is off the record, is off the record," Gary told him.

"There's so much of it," rumbled the doctor, "that sounds like sheer dream stuff.”

"Hell," said Evans, "there always is in everything new. My ships sound like it, too. But the thing will work. I know it will.”

Kingsley perched himself on a heavy kitchen chair.

"It started more than a year ago," he said. "We were studying the cosmics.

Elusive things, those rays. Men have studied them for about five thousand years and they still don't know as much about them as you think they would after all that time. We thought at first that we'd made a really astounding discovery, for our instruments, used on top of the building, showed that the rays came in definite patterns. Not only that, but they came in definite patterns at particular times. We developed new equipment and learned more about the pattern. We learned that it occurred only when Pluto had rotated into such a position that this particular portion of the planet was facing the Great Nebula in Andromeda. We learned that the pattern, besides having a certain fixed physical structure, also had a definite time structure, and that the intensity of the bombardment always remained the same. In other words, the pattern never varied as to readings; it occurred at fixed intervals whenever we directly faced the Great Nebula, and the intensity varied very slightly, showing an apparent constant source of energy operating at specific times. In between those times our equipment registered the general haphazard behavior one would expect in cosmic rays.”

The doctor rumbled on: "The readings had me down. Cosmic simply shouldn't behave that way. There never had been any instance of their behaving that way at any time before. Of course, this was the first thorough investigation far from the Sun's interfering magnetic fields. But why should they behave in that manner only when we were broadside to the Great Nebula?

"My two assistants and I worked and studied and theorized and it finally came down to just one thing. The things we were catching with our instruments weren't cosmic rays at all. They were something else. Something new. Some strange impulse coming to us from outer space. Almost like a signal. Like something or someone or God-knows-what was signaling to someone or something stationed here on Pluto. We romanticized a bit. We toyed with the idea of signals coming from another galaxy, for you know the Great Nebula is an exterior galaxy, a mighty star system, some nine hundred million light years across intergalactic space.

"But that was just imagining. There was nothing to support it in the light of factual evidence. We still aren't sure what it's all about, although we know a great deal more now than we did then.

"The facts we did gather, you see, indicated that whatever we were receiving must be definite signals, must originate within some sort of intelligence. Some intelligence, you see, that would know just when and where to send them. But there was the problem of distance. Just suppose for a moment that they were coming from the Great Nebula. It takes light almost a billion years to reach us from the Nebula. While it is very probable that the speed of light can be far exceeded, there is little reason to believe at present than anything could be so much faster than light that signaling could be practical across such enormous space. Unless, of course, the matter of time were mixed up a little, and when you get into that you have a problem that takes more than just a master mind. There was just one thing that would seem a probable answer… that if the signals were being sent from many light years distant, they were being routed through something other than all that space. Perhaps through another continuum of space-time, through what you might call, for the want of a better term, the fourth dimension.”

"Doctor," said Herb, "you got me all balled up.”

Dr. Kingsley's chuckle rumbled through the room.

"It had us that way, too," he said. "And then we figured maybe we were getting pure thought. Thought telepathed across the light years of unimaginable space. Just what the speed of thought would be no one could even guess. It might be instantaneous… it might be no faster than the speed of light… or any speed in between the two. But we do know one thing: that the signals we are receiving are the projection of thought.

Whether they come straight through space or whether they travel through some shortcut, through some manipulation of space-time frames, do not know and I probably will never know.

"It took us months to build that machine you saw in the other room.

Briefly, it picks up the signals, translates them from the pure energy of thought into actual thought, into symbols our mind can read. We also developed a method of sending our own thoughts back, of communicating with whatever or whoever it is that is trying to talk with Pluto. So far we haven't been successful in getting an entire message across. However, apparently we have succeeded in advising whoever is sending out the messages that we are trying to answer, for recently the messages have changed, have a note of desperation, frantic command, almost a pleading quality.”

He brushed his coat sleeve across his brow.

"It's all so confusing," he confessed.

"But," asked Herb, "why would anyone send messages to Pluto? Until men came here, there was no life on the planet. Just a barren planet, without any atmosphere, too cold for anything to live. The tail end of creation.”

Kingsley stared solemnly at Herb.

"Young man," he said, "we must never take anything for granted. How are we to say there never was life or intelligence on Pluto? How do we know that a great civilization might not have risen and flourished here aeons ago? How do we know that an expeditionary force from some far-distant star might not have come here and colonized this outer planet many years ago?”

"It don't sound reasonable," said Herb.

Kingsley gestured impatiently.

"Neither do these signals sound reasonable," he rumbled. "But there they are. I've thought about the things you mention. I am damned with an imagination, something no scientist should have. A scientist should just plug along, applying this bit of knowledge to that bit of knowledge to arrive at something new. He should leave the imagination to the philosophers. But I'm not that way. I try to imagine what might have happened or what is going to happen. I've imagined a mother planet groping out across all space, trying to get in touch with some long-lost colony here on Pluto. I've imagined someone trying to re-establish communication with the people who lived here millions of years ago. But it doesn't get me anywhere.”

Gary filled and lit his pipe, frowning down at the glowing tobacco. Voices in space again. Voices talking across the void. Saying things to rack the human soul.

"Doctor," he said, "you aren't the only one who has heard thought from outer space.”

Kingsley swung on him, almost belligerently. "Who else?" he demanded.

"Miss Martin," said Gary quietly, puffing at his pipe. "You haven't heard Miss Martin's story yet. I have a hunch that she can help you out.”

"How's that?" rumbled the scientist.

"Well, you see," said Gary, softly, "she's just passed through a thousand years of mind training. She's thought without ceasing for almost ten centuries.”

Kingsley's face drooped in amazement.

"That's impossible," he said.

Gary shook his head. "Not impossible at all. Not with suspended animation.”

Kingsley opened his mouth to object again, but Gary hurried on. "Doctor,”

he asked, "do you remember the historical account of the Caroline Martin who refused to give an invention to the military board during the Jovian war?”

"Why, yes," said Kingsley. "Scientists have speculated for many years on just what it was she found — ”

He started out of his chair.

"Caroline Martin!" he shouted. He looked at the girl.

"Your name is Caroline Martin, too," he whispered huskily.

Gary nodded. "Doctor, this is the woman who refused to give up that secret a thousand years ago.”