WHEN John Gordon first heard the voice inside his mind, he thought that he was going crazy.

It came first at night when he was just falling asleep. Through his drowsing thoughts, it spoke sharp and clear.

“Can you hear me, John Gordon? Can you hear me call?”

Gordon sat up, suddenly wide awake and a little startled. There had been something strange and upsetting about it.

Then he shrugged. The brain played strange tricks when a man was half asleep and the will relaxed. It couldn't mean anything.

He forgot it until the next night. Then, just as he began to slip into the realm of sleep, that clear mental voice came again.

“Can you hear me? If you can hear me, try to answer my call!”

Again Gordon woke up with a start. And this time he was a little worried. Was there something the matter with his mind? He had always heard it was bad if you started to hear voices.

He had come through the war without a scratch. But maybe those years of flying out in the Pacific had done something to his mind. Maybe he was going to be a delayed psychoneurotic casualty.

“What the devil, I'm getting excited about nothing,” Gordon told himself roughly. “It's just because I'm nervous and restless.”

Restless? Yes, he was that. He had been, ever since the war ended and he returned to New York.

You could take a young accountant clerk out of a New York insurance office and make him into a war pilot who could handle thirty tons of bomber as easily as he handled his fingers. You could do that, for they had done it to Gordon.

But after three years of that, it wasn't so easy to give that pilot a discharge button and a “thank you” and send him back to his office desk. Gordon knew that, too, by bitter experience.

It was queer. All the time he had sweated and risked his neck out there over the Pacific, he had been thinking how wonderful it would be to get back to his old job and his comfortable little apartment.

He had got back, and they were just the same as before. But he wasn't. The John Gordon who had come back was used to battle, danger and sudden death, but not used to sitting at a desk and adding up figures.

Gordon didn't know what he wanted, but it wasn't an office job in New York. Yet he'd tried to get these ideas out of his mind. He'd fought to get back into the old routine, and the fight had made him more and more restless.

And now this queer calling voice inside his brain! Did that mean that his nervousness was getting the best of him, that he was cracking up?

He thought of going to a psychiatrist, but shied at the idea. It seemed better to fight down this thing himself.

So the next night, Gordon grimly waited for the voice to call and prepared to prove to himself that it was all delusion.

It did not come that night, nor the next. He supposed it was over. Then the third night, it came more strongly than ever.

“John Gordon, listen to me! You are not having delusions! I am another man, speaking to your mind by means of a science I possess.”

Gordon lay there in semi-sleep, and that voice seemed wonderfully real to him.

“Please try to answer me, John Gordon! Not with speech, but with thought. The channel is open-you can answer if you try.”

Dazedly, Gordon sent an answering thought out into the darkness.

“Who are you?”

The reply came quickly and clearly, with a pulse of eagerness and triumph in it.

“I am Zarth Arn, prince of the Mid-Galactic Empire. I speak to you from two hundred thousand years in your future.”

Gordon felt vaguely aghast. That couldn't be true! Yet that voice was so real and distinct in his mind.

“Two hundred thousand years? That's insane, impossible, to speak across a time like that. I'm dreaming.”

Zarth Arn's reply came quickly. “I assure you that it is no dream and that I am as real as you are, even though two thousand centuries separate us.”

He went on. “Time cannot be crossed by any material thing. But thought is not material. Thought can cross time. Your own mind travels a little into the past every time that you remember something.”

“Even if it's true, why should you call me?” Gordon asked numbly.

“Much has changed in two hundred thousand years,” Zarth Arn told him. “Long ago, the human race to whose first era you belong spread out to the other stars of the galaxy. There are great star-kingdoms now, of which the greatest one is the Mid-Galactic Empire.

“I am high in that Empire, and am a scientist and seeker of truth above all else. For years, I and a colleague have been delving into the past by throwing my mind back across the ages, groping and making contact with minds of men whose spirits are attuned to my own.

“With many of those men of the past, I have temporarily exchanged bodies. The mind is a webwork of electrical energy which inhabits the brain. It can be drawn by suitable forces from the brain, and another electric webwork, another mind, installed in its place. My apparatus can accomplish that by sending my whole mind instead of just a thought-message into the past.

“Thus my mind has occupied the body of a man of past ages, while his mind was simultaneously drawn across time to inhabit my body. In that way, I have lived in and explored the history of many different eras of past human history.

“But I have never gone so far back in time as your own remote era. I want to explore your age, John Gordon. Will you help me? Will you consent to a temporary exchange of bodies with me?”

Gordon's first reaction was a panicky refusal. “No! It would be ghastly, insane!”

“There would be no danger,” Zarth Arn insisted, “You would merely spend some weeks in my body in this age, and I in yours. And then Vel Quen, my colleague here, would effect a re-exchange.

“Think, John Gordon! Even as it would give me a chance to explore your long-dead age, so would it give you a chance to see the wonders of my time! “I know your spirit, restless, eager for the new and unknown. No man of your age has ever been given such a chance to plunge across the great gulf of time into the future. Will you reject it?”

Suddenly Gordon felt caught by the glamour of the idea. It was like a wild bugle-call summoning to adventure hitherto undreamed.

A world and universe two thousand centuries in the future, the glories of a star-conquering civilization-to behold all that with his own eyes?

Was it worth risking life and sanity for? If all this was true, was he not being offered a supreme chance at the adventure for which he had been so restlessly longing?

Yet still he hesitated. “I wouldn't know anything about your world when I awoke in it,” he told Zarth Arn. “Not even the language.”

“Vel Quen would be here to teach you everything,” the other answered quickly. “Of course, your age would be equally strange to me. For that reason, if you agree, I should want you to prepare thought-spools from which I could learn your language and ways.”

“Thought-spools? What are they?” Gordon asked, puzzled.

“They are not yet invented in your age?” said Zarth Arn. “In that case, leave me some childrens' picture-books and dictionaries for learning your language and some sound-records of how it is spoken.”

He continued. “You don't need to decide at once, John Gordon. Tomorrow I'll call you again and you can give me your decision then.”

“Tomorrow I'll think that all this has just been a crazy dream,” Gordon said.

“You must assure yourself that it is no dream,” Zarth Arn said earnestly. “I contact your mind when you are partly asleep because then your will is relaxed and the mind is receptive. But it is no dream.”