He found Big Tim standing upon a short ramp before a section of the wall which was different from the rest. It was a dark area, rectangular in shape. At one side, seen dimly through the strange green substance, was an arrangement of rods and gears which was obviously an operating mechanism. Protruding from a slot in the wall, and clearly connected with the mechanism, was a short lever.

Big Tim's blue eyes glittered with daring. His tow hair awry, he looked more than ever the picture of an overgrown, impulsive boy.

"Good heavens, guy, you surely don't intend to go in there!" Nellon exclaimed. "We don't know what sort of—"

Big Tim gave a short, excited laugh. "Look—there's nothing to be afraid of. There's just that green light up there and the people, and they are dead. Everything in this place is dead. Brad, this is the chance of a lifetime. We'll be the first to look upon the faces of an extra-terrestrial race since the Martians."

Big Tim pulled the opening lever. There was a moment of appalled and complete quiet. Then hidden motors hummed into alien life, and slowly the door before them slid aside. Undimmed now by its confining walls, the green radiance poured through the opening in a blinding flood.

"Come on," Big Tim urged. And without any hesitation on his own part, he stepped through, to be bathed instantly in the emerald glow.

Nellon moved to the open doorway. The emerald rays from the globe fell upon him with an almost sensible warmth. Again that weird peace and comfort was upon him, but more overpoweringly now. He felt a rising tide of drowsiness. In some strange way, he knew it would be good to allow himself to succumb to the softly-blanketing darkness which was filling his mind. It would be a blessed surcease from all the troubles and cares of his present world. But something held him back.

And though a great, calm voice seemed to give him every assurance of safety, a stubborn, small one screamed him its warning. In a turmoil, he watched Big Tim stride toward the nearest of the platforms.

It became evident to Nellon almost immediately that Big Tim was never going to reach his goal. For shortly after the first several steps, the blonde giant's purposeful walk slowed to a bemused shamble. And, watching with a curiously disembodied attention, Nellon saw him waver, stop, and then collapse upon the floor, as though he had suddenly become very, very tired.

The warning voice was shrieking now. Nellon felt a swift rush of terror that ripped him free of the force which enclosed him in its lulling folds. He shot a wide-eyed glance from the gleaming, inert shape of Big Tim's suit to the globe flaming high above. He wanted suddenly to run.

He struggled in panic against the invisible bonds of peace and comfort which were so reluctant to let him go. His determination to be free was the fierce and frenzied one of utter fear. Flailing his arms as if against some material foe, he managed to stumble down from the ramp, to one side of the doorway where the green light would not reach him.

Exhausted from the herculean struggle, he slumped to the floor. A soft, warm blackness was settling over him, and he was powerless to fend it off. But he knew that he was safe, and the satisfaction which he felt was increased by the radiation which he had absorbed, so that when he finally swooped into unconsciousness, it was amidst a thunderous, victorious singing.

Nellon's next sensations were curious ones. He seemed to awaken in another realm. It was a vast and formless place with no distinguishable feature or color, but it was curiously sentient, pulsing with awesome possibilities.

Now, as though stirred by his reflection upon it, the nebulous stuff began to writhe. And then, taking shape from the formless jumble of thoughts in his subconscious, a dream-world began to grow. Bits were added here, others discarded there, but every compartment in the storehouse of his mind contributed something. And all assembled in accordance with the pattern Nellon had fashioned in two and a half years of brooding. Finally his dream paradise was complete to the last detail of his hopes and imaginings.

It was the world which he had built around Laura taken on an immaterial, but to him nonetheless real, life. There was Laura and there was himself. And there was the complete bliss for which he had planned Big Tim's murder to achieve.

He became aware of a change. The outlines of his world were dimming, dissolving, fading. Even Laura, radiantly lovely, was beginning to blur before his eyes.

In horror he sought to clutch the evaporating structure to him and stabilize it once again. But it slipped through his fingers like an impalpable mist. Before he was fully alive to it, his dream Eden was gone, and he was back in that formless void in which he had found himself. And even that was thinning.

Nellon awoke. He looked around for Laura and that idyllic dream land in which they had loved. But only the great, green cylinder with its flaming globe and the vast room beyond met his gaze.

Nellon climbed to his feet. With the action, he became aware that he felt wonderfully refreshed and stimulated. He looked around for Big Tim, then he remembered. Avoiding the open doorway through which the rays still poured, he peered through the green wall. Big Tim was lying there on the floor within. He was very still in his thermalloy suit.

Nellon began a chain of reasoning. As it progressed, there went with it a rising tide of exultation.

As long as Big Tim remained there under the influence of the globe, he would remain unconscious, living, perhaps, a dream as real and vivid as his own had been. It would be just as though Big Tim were dead. None of the expedition members knew of the doorway through which he and Big Tim had entered. With the almost continuous storms which raged on Titan, the door would soon become covered again. Ages might pass before a chance accident revealed it once more.

He, Nellon, could go back to the ship with a tale of how he had lost Big Tim in the bitter storm. The men might search, but he knew it would be futile.

Laura would grieve, of course, when he returned and told her the news. But he would be there to comfort her, and she would get over it. And he knew that she would marry him, with Big Tim out of the way. He could look forward to a happiness more satisfying than that of the dream.

Nellon saw his course clear. He knew just what he had to do.

First he released the lever, and the door slid shut, entombing Big Tim within the great cylinder. Then he retraced his way down to the lower level and through the maze of rooms and corridors. It was not long before the snow of Titan once more keened against his suit.

He threw his weight against the great door. Only the impulse was necessary to close it, for the operating mechanism hummed into vibrant life and it swung shut where it had not been shut before—and locked! Nor would it open again.

Even if he had wanted to re-enter, that was impossible.

Nellon started back to the ship. With the curious vigor he felt, the dangers and difficulties of the return trip hardly registered upon him at all. Gone was his sullen dislike of the ever-raging storm. He plowed through it with a careless smile, fighting his way over the wild and tumbled terrain. And it was with no feeling of exhaustion at all that he finally sighted the great, toothed ice ridge which marked the site of the camp.

As Nellon shouldered through the narrow cleft which led into the protected, tiny valley, he remembered to remove the smile of eager triumph upon his face. It would not go with the story he was to tell.

But it was hardly necessary for him to make the effort. For at the sight that met his eyes, an involuntary grimace of appalled amazement flashed over his features.

Where the ship had rested there now was nothing at all, save a smooth surface of snow. And to his incredulously searching gaze, there was no