himself wheeled a strange electrical apparatus into position in front of the glass. Then took up a position behind a large glass screen, and motioned Mark to join him.

"What are you going to do?"

"You shall see!"

The white-haired savant threw a switch. The laboratory's lights went out. He pressed a button on the control board of the apparatus behind which they stood. Leaned forward eagerly, peering through the glass screen at the mirror. Manipulated dials and levers.

An inexplicable excitement gripped Mark. He had a sudden, unshakable conviction that he and the professor were on the verge of incredible discoveries. Discoveries that would lead him to an explanation of the strange coma that held Elaine in its grim sway.

His brown eyes fastened on the mirror. The next instant they went wide with astonishment.

The glass screen behind which he and the professor were standing was clearly reflected.

But it was merely an opaque surface! Neither he nor the scientist could be seen behind it!

As if reading his mind, Professor Duchard gave vent to a little laugh.

"'One-way' glass," he explained. "It permits vision in only one direction." Then the humor went out of his voice. "We may thank God that science developed it before we are through."

Again he leaned forward, his eyes on the mirror.

An instant later he leveled a quivering forefinger.

"Look!"

There, in the semi-darkness where stood the looking-glass, a weird figure was beginning to glow!

Tension flooded through Mark's veins. His fingers knotted into fists. His eyes strained to catch the thing which grew upon the mirror's surface.

Slowly, like some wizard's evil phantasmagoria, the glowing lines came together. Took form. Painted a figure—

The figure of the woman in the mirror!

"That's her!" he cried excitedly. "That's the woman we saw reflected instead of Elaine!"

Professor Duchard snapped off the machine beside him. He turned on the lights. Swung around to face his daughter's fiance. His face was grey. Grim lines of worry etched deep into the flesh.

"So that is it!" he said. "That is what he has done to her!"

There was fear in his voice ... living, breathing fear. That and despair. The despair of utter hopelessness. His shoulders sagged with it. The sparkle had gone out of his eyes.

Mark gripped the old man's arm. Blood lust flamed in his own brown orbs. Every muscle was taut. The cords in his neck stood out like knotted ropes.

"What is it?" he demanded savagely. "Is it Vance? What has he done to her?"

Wearily, the scientist pulled his arm away and gestured the other to a seat.

"I shall tell you," he said. "You will not believe me, but I shall tell you."

"Yes. Go on. I'll decide for myself whether I'll believe you or not."

The professor stared into Mark's eyes.

"How much do you know about time?" he demanded.

"Time?"

"Yes. And time travel."

The younger man shrugged.

"Practically nothing," he admitted. "Oh, I've read a few stories, of course. But that's all. I don't know what the theory of it all is, if that's what you mean."

"I thought so." Professor Duchard sighed. "That being the case, there is little use in my wasting energy trying to give you any real understanding of it.

"However, I can tell you this: time is not the immutable thing most people presume it to be. Actually, it is only another dimension. As a research physicist, I have for many years been convinced of this."

"You mean that time travel really is possible? That men can be transported into the future or the past—"

The other held up a restraining hand.

"Yes. Time travel is possible, if men could break through into that other dimension." A pause. "Yet up until tonight, I never believed that man had found a way to pass that barrier."

"But professor! Think what you're saying! You're telling me that I could go back and murder my own grandfather. That I could prevent myself from being born—"

Again the elder man sighed.

"I was afraid of this," he said. "I knew you could not understand." He hesitated. Then: "At any rate, take my word for it that time travel is possible. Also, I assure you that there are any number of perfectly sound theoretical and practical reasons why you never could hope to murder your grandparents."

The other brushed the words aside.

"What about Elaine? What's all this got to do with her?"

"Everything. You see, my boy, it is not possible for us to transport our material bodies across time. They cannot bridge the gap. They must remain in the period in which they are born—"

"But Elaine—"

Never had Mark seen the white-haired savant so solemn. His aged face was drawn with worry. Yet there was terrifying self-confidence in his words.

"Elaine," he said quietly, "at this moment is trapped in time!"

There was a moment of stunned silence, then. Mark's brain was spinning. He stared at Professor Duchard through narrowed eyes, half-convinced that the man was mad. And yet—

"I am not insane," the scientist declared, as if answering an unspoken question. "Believe me, my boy, I am not."

"Go on."

"That mirror which Adrian Vance sent to my daughter actually is a crude time machine. A device for transporting a human soul to another period. Who devised it I cannot say. I believe it is old, and that Vance came upon it only by chance."

"But it isn't a machine. It's just a mirror—"

"Yet it is the gate through which a mind may be reflected into past or future. All that is needed is a focal point. A person to receive that mind. In this case, Adrian Vance made the focal point one of my ancestors, the first Elaine Duchard."

"The first Elaine Duchard!"

"Yes. She was the woman in the picture. And the woman whose image we now find imprinted in that devil's mirror."

"But how—"

"You remember how Adrian Vance swore vengeance when Elaine refused to marry him." The aged savant's voice choked with anger. "This must be what he planned. He bought the picture Gustav Jerbette painted of my ancestor. Then, by some process, imprinted her portrait in the center of this mirror, whose secret he somehow discovered. Apparently the picture does not show except at a certain angle. Perhaps only my daughter's coloring or facial configuration would ordinarily bring it out." He shrugged. "That I do not know."

Mark nodded slowly. He was breathing hard, his eyes dark with anger.

"At any rate," the other continued, "Elaine tonight looked into the mirror. By some accident—an accident Vance had counted on taking place eventually, of course—, she happened to get exactly the right angle. She saw her ancestor. Her mind flashed back through time, into that other Elaine Duchard's brain—"

And then, all at once, the old man's iron will cracked.

"She is trapped!" he cried in a voice like the wail of a north wind through the pines. "She is trapped in the body of that first Elaine Duchard, while her own lies here, a useless, unconscious husk! She will die, as our ancestor died—"

"What do you mean? How did the first Elaine Duchard die?" Mark was on his feet, fists clenched.

Professor Duchard sat slumped forward, his face buried in his hands, white hair awry.

"She was a tragic figure," he mumbled. "You saw her picture. You know how beautiful she was.

"She came from a minor family of the French nobility, but she loved a young Jacobin—a man such as those who, a few years later, overthrew the monarchy and founded the French republic.

"She had another suitor, however. A Baron Morriere. When he learned that she was going to marry another, he kidnapped her the night before her wedding. Her lover was present at the time, and was nearly killed trying to protect her. Later he returned to help her escape from the Chateau Morriere. They succeeded