and began firing questions at me again, going over the ground we had covered, to check up on his information. I was amazed at the uncanny accuracy with which he had grasped such a great mass of technical detail. It had taken me years of study to pick up what he had taken from me, and apparently retained intact, in something more than an hour, Earth time.

  glanced at the Earth-time clock on the wall of the navigating room as he triumphantly finished his questioning. Less than an hour remained before the time set for our return trip.

"I'm sorry," I commented, "to be an ungracious host, but I am wondering what your plans may be? You see, we are due to start in less than an hour, and—"

"A passenger would be in your way?" Harbauer smiled as he uttered the words, but there was a gleam in his long eyes that rather startled me, and I wondered if I only imagined the steeliness of his voice. "Don't let that worry you, sir."

"It's not worrying me," I replied, watching him closely. "I have enjoyed a very remarkable, a very pleasant experience. If you should care to remain aboard the Ertak, I should like exceedingly to have you accompany us to our Base, where I could place you in touch with other laboratory men, with whom you would have much in common."

Harbauer threw back his head and laughed—not pleasantly.

"Thanks!" he said. "But I have no time for that. They could give me no knowledge that I need, now; you have told me and showed me enough. I understand how you have released atomic energy; it is a matter so simple that a child should have guessed it, and man has wondered about it for centuries, knowing that the power was there, but lacking a key to unfetter it. And now I have that key!"

"True. But perhaps our scientists would like, in exchange, the secret of moving forward in time," I suggested, reasonably enough.

"What do I care about them?" snapped Harbauer. He loosened the cord of the robe with a quick, impatient gesture, as though it confined him too tightly, and threw the garment from him.

hen, suddenly, he took a quick stride toward me, and thrust out his ugly head.

"I know enough now to give me power over all my world," he cried. "Haven't you guessed the reason for my interest in your engines of destruction? I came down the centuries ahead of my generation so that I might come back with power in my hand; power to wipe out the fools who have made a mock of me. And I have that power—here!" He tapped his forehead dramatically with his left hand.

"I will bring a new regime to my era!" he continued, fairly shouting now. "I will be what many men have tried to be, and what no man has ever been—master of the world! Absolute, unquestioned, supreme master!" He paused, his eyes glaring into mine—and I knew from the light that shone behind those long, narrow slits, that I was dealing with a madman.

"True; you will," I said gently, moving carelessly toward the microphone. With that in my hand, a slight pressure on the General Attention signal, and I would have the whole crew of the Ertak here in a moment. But I had explained the workings of the navigating room's equipment only too well.

"Stop!" snarled Harbauer, and his right hand flashed up. "See this? Perhaps you don't know what it is; I'll tell you. It's an automatic pistol—not so efficient as your disintegrator-ray, but deadly enough. There is certain death for eight men in my hand. Understand?"

"Perfectly." What an utter fool I had been! I was not armed, and I knew that Harbauer spoke the truth. I had often seen weapons similar to the one he held in the military museums. They are still there, if you are curious—rusty and broken, but not unlike our present atomic pistols in general appearance. They propelled the bullet by the explosion of a sort of powder; inefficient, of course, but, as he had said, deadly enough for the purpose.

ood! You are a good sort Hanson, but don't take any chances. I'm not going to, I promise you. You see,"—and he laughed again, the light in his long eyes dancing with evil—"I'm not likely to be punished for a few killings committed centuries after I'm dead. I have never killed a man, but I won't hesitate to do so now, if one—or more—should get in my way."

"But why," I asked soothingly, "should you wish to kill anyone? You have what you came for, you say; why not depart in peace?"

He smiled crookedly, and his eyes narrowed with cunning.

"You approve of my little plan to dominate the world?" he asked softly, his eyes searching my face.

"No," I said boldly, refusing to lie to him. "I do not, and you know it."

"Very true." He pulled out his watch with his left hand, and held it before his eyes so that he could observe the time without losing sight of me for even an instant. "I doubted that I could secure your willing cooperation; therefore, I am commanding it.

"You see, there are certain instruments and pieces of equipment that I should like to take back to my laboratory with me. Perhaps I would be able to reproduce them without models, but with the models my task will be much easier.

"The question remaining is a simple one: will you give the proper orders to have this equipment removed to the spot where you first saw me, or shall I be obliged to return to my own era without this equipment—leaving behind me a dead commander of the Special Patrol Service, and any other who may try to stop me?"

  tried to keep cool under the lash of his mocking voice. I have never been adept at holding my temper when I should, but somehow I managed it this time. Frowning, I kept him waiting for a reply, utilizing the time to do what was perhaps the hardest, fastest thinking of my life.

There wasn't a particle of doubt in my mind regarding his ability to make good his threat, nor his readiness to do so. I caught the faint glimmering of an idea and fenced with it eagerly.

"How are you going to go back to your own period—your own era?" I asked him. "You told me, I believe, that it was impossible to move backward in time."

"That's not answering my question," he said, leering. "Don't think you're fooling me! But I'll tell you, just the same. I can go back to my own era: that is, back to my own actual existence. I shall return just two hours after I leave; I could not go back farther than that, and it's not necessary that I do so. I can go back only because I came from that present; I am not really of this future at all. I go back from whence I came."

"But," I objected, thinking of something I had read in the clipping he had showed me, "you're not going back to your own era. You cannot. If you returned, you would put your project into execution, and history does not record that activity." I saw from the sudden narrowing of his abnormally long eyes that I had caught his interest, and I pressed my advantage hastily. "Remember that all the history of your time is written, Harbauer. It is in the books of Earth's history, with which every child of this age, into which you have thrust yourself, is familiar. And those histories do not record the domination of the world by yourself. So—you are confronted by an impossibility!"