"Well, keep your eyes peeled for Tower Point up there. As soon as we've got old Ryska's junk, we'll all be heading for home."

Nellon felt a weary sort of satisfaction. No, Big Tim didn't suspect. Big Tim didn't know that he was never going home again. Nellon had accompanied him on this final little trip to make sure of that.

They were nearing the lower end of a long ravine. Here, the invisible trail which they followed rose steeply and entered a narrow cleft between two huge slabs of ice. Then it dipped around the base of a great pinnacle, which thrust like an undaunted finger into the rage of the storm. This was the unique landmark which the expedition members had christened Tower Point.

Tower Point served as a great, white warning signal. For the trail skirting it gave way abruptly from powdery snow to ice of mirror slickness and slanted down sharply to a frozen lake which, unsheltered from the terrible wind, was polished constantly. One end of the lake had once been a falls, for here it ended, dropping down as sheerly as a precipice for hundreds of feet.

The way around Tower Point was one of the chief dangers, for there was no telling where the snow ended and the ice began. A sudden slip meant a swift slide down and onto the frozen surface of the lake. There, where the wind swept in all its unbroken force, one would be blown helplessly over the icy edge of the falls and dashed to death on the jagged ice teeth far below. d.i.c.k Fulsom, metallurgist, had already lost his life that way.

And that was the way Nellon had planned Big Tim Austin would die. Tower Point would mark the scene of another tragedy. Just the merest of shoves on that deadly borderline between ice and snow, and Big Tim would go flas.h.i.+ng down to the lake and over the falls.

It was as simple as that. Nellon knew that nothing could ever be proved against him. Nor would the faintest thought of suspicion ever enter the minds of the others. For to them he and Big Tim had always been pals in the truest, deepest sense of the word.

No, he had nothing to fear. The only reckoning would be with his conscience, but he did not allow that to trouble him now, for all he wanted to think of was Laura. Laura would be his. He knew that with a grim, satisfying certainty.

Now they were starting up the difficult rise which led to Tower Point. Nellon slipped gradually behind, until he walked in Austin's rear. His eyes settled and fixed to the metal back of the other's suit.

Very soon, now, it would be over. And then he would be on his way back home to Earth. Laura would be there on Earth, waiting. Laura.

Laura had silky chestnut hair that glinted with deep, red lights and fell in thick curls to her shoulders. Her eyes were very brown and level and filled with dancing motes of laughter. Her nose was short and pert, and he remembered the tiny mole which lay like a speck of soot just near the left nostril. Her lips were a little too wide, but they were firm and full and could quirk up in a smile that was rich and warming. Her body was small and sweet in the gentle swelling of its curves.

But it was her smile which Nellon thought of now. A bitter pain shot through him as he recalled it. Though in his thoughts it was all for him, he knew that its actual warmth was shed upon Tim Austin. Big Tim, who was so large and happy and tousled that he looked like an overgrown boy.

It was together that they had met Laura. And it was together that they had dated her. But as the three-sided friends.h.i.+p deepened, the inevitable change had occurred.

Strangely enough, it had been Nellon himself who brought it about. It had happened the evening he had had Laura with him alone for the first time. The spell of her charm had been concentrated upon him alone, and he had lost his head to such an extent that he proposed.

Laura had said no, and things had never been the same between them again. Though Big Tim may have wondered at times, he hadn't been sensitive enough to realize the change. Nellon had, in fact, concealed his pain and desire so effectively that Big Tim had never awakened to the truth.

Nellon remembered almost the exact words Laura used that evening. Even now the tones of her voice rang in his ears, gentle and sad.

"I'm sorry, Brad," she had said. "Please try to understand. I really do like you--an awful lot. You're like a rock, solid and strong, something to cling to. But Tim is like a big, clumsy playful dog--so terribly lovable. I can't help it. Really, Brad, if it wasn't for Tim, I'd never hesitate to marry you."

For two and a half years her words had drummed in his mind. "If it wasn't for Tim--"

At first he had tried to ignore the early thoughts of murder which had crept insidiously into his brain. But they persisted, grew stronger, and before long he had been making actual plans. Several times the cold hand of death had reached for Tim Austin, but each time Nellon's instincts had revolted and the thing had remained undone.

But now the members of the expedition were preparing to return home to Earth. Nellon knew that if Big Tim reached Earth alive the Laura he remembered and wanted would be lost to him forever. If Big Tim was to die, it would have to be done before the s.h.i.+p left, for once sealed within its confines, the risks would be too overwhelmingly large.

It had been old Sigmund Ryska who had presented Nellon with what he had realized was his final and only chance. Old Ryska had left several pieces of valuable scientific equipment lying in a small hut which he had set up for some experiments. He had remembered them at the last moment. Someone had to fetch them before leaving, and Big Tim Austin had volunteered. Nellon, because of the purpose which motivated him, had gone along.

He had made up his mind at last. This time he would allow no scruples to stay his hand. This time Big Tim would die.

They had reached Tower Point. Nellon's breathing had quickened, and a fine perspiration had broken out upon his face. Fine lines were etched around his eyes and mouth.

Nellon and Austin stood side by side a moment upon the summit which was crowned by the great pinnacle of Tower Point. Down below glittered the surface of the frozen lake. White and desolate, the frozen wastes of t.i.tan tumbled and leaped on every side. Snow swirled about them, whipped into angry life by the gale.

Austin turned.

"Well, down we go. Watch it, guy." For a second his eyes locked with Nellon's. A frown of perplexity and concern narrowed them.

"Brad--anything wrong? You don't look right, somehow."

Nellon felt himself go icy cold. Words of hoa.r.s.e denial tumbled to his lips.

"No--it's nothing. I--I'm all right."

But Big Tim was not a.s.sured.

"Listen, Brad, Ryska's hut isn't much further, now. You'd better wait here, and I'll go on ahead and get the stuff. It's hard and dangerous going, and if you aren't well--"

"I tell you I'm all right!" Nellon blurted. He was hot now with a feverish warmth that made the perspiration which covered his body feel clammily cold. The old fear of murder was gone. Nellon knew only a burning desire to get the thing done, a wild alarm that his opportunity would vanish before he got the chance.

Big Tim shrugged.

"Come on, then. But watch it, guy, and sing out if you need me." With a last troubled glance at Nellon, he turned to the downward sloping trail and began the descent. He moved slowly and carefully, testing each foot of the way with a ponderous, insulated boot for the sudden slickness that would announce the dangerous ice.

Nellon was swept with relief. His blood rushed through his veins in a sudden fierce singing. Now, now! The broad, metal back of Big Tim's suit spread before him. Far down below the gleaming ice waited.

Nellon took swift steps forward, his arms coming up. The rus.h.i.+ng in his ears leaped to a high pitch. He sucked in a breath, held it. Then-- Nellon slipped. It must have been a small patch of ice undetected by Austin. But Nellon slipped, lost balance, crashed into the other. Together they went whizzing down the trail toward the frozen lake. It was a long slide, but incredibly swift, and confusion and surprise made it seem all the shorter. What happened took place too quickly for thought to follow or prevent.

They caromed onto the ice of the lake. With a gleeful, demoniac howl, the terrible wind swooped down upon them, swept them with increased speed toward the edge of the falls. Though still half stunned by the sudden catastrophe, they reacted with the instinct of long conditioning, tried frantically to r.e.t.a.r.d their swift flight over the ice. But it was futile. Their gouging metal fingers could find no purchase in the gla.s.sy smoothness over which they sped. And before friction could slow them even the merest of trifles, they were swept over the edge of the falls.

They went over, but not down upon the jagged ice teeth bared hungrily below. Nellon's attempted shove had given them both an added impetus, and they had shot over the ice at an angle which landed them upon the snow banked on the farther side of the gorge.

In that far distant day when the heat of Saturn had been great enough to cloak its satellites in warmth, the gnawing of the falls had worn steep sides in the gorge. And though the snow upon which the two men had fallen was thick and soft, it was not enough to hold them, and they went rolling end over end, in great clouds of powdery white, to stop only when they had reached the bottom.

[Ill.u.s.tration: Helplessly the two men hurtled down the snowy slope]

For long moments they lay still. A thick pall of settling snow hung on the frigid air. The wind seized portions of this and sent them whirling and twisting in fantastic gyrations.

The thermalloy suits were essentially compact, mobile shelters, and had been designed more for protection against inimical extra-terrestrial elements rather than for comfort. Brad Nellon had been bruised and shaken until it seemed that his body was one throbbing ache. His senses whirled giddily in a black mist shot through with flames of pulsing red.

Of a sudden the pain leaped to intolerable heights. His battered muscles screamed an anguished protest along his nerves. Then the pain was gone, and momentarily the blackness closed in again. But something like a fresh wind sprang up, and sent the engulfing fog thinning away. Nellon's brain cleared. He opened his eyes.

He looked into Big Tim's face. Big Tim was bending over him, worried and anxious. Nellon began to understand.

Big Tim had recovered first from the plunge. He had propped Nellon up, then turned the valve which increased the flow of oxygen inside his suit. They were alive. Nellon felt a dull wonder at it.

"Brad--all right?" It was Big Tim, his voice strained and hoa.r.s.e.

Nellon nodded mechanically.

"All right."

"What happened, Brad?"

Nellon looked away. He looked up the gorge, at the tip of Tower Point. He licked his lips.

"I--I don't know. Didn't feel well--slipped on a patch of ice."

Big Tim shook his head.

"I told you to stay up there, didn't I? I knew you were in no condition to make the descent, but you were just stubborn enough to do so. It's lucky we didn't get our necks broken." He looked down and across to where, directly under the falls, the ice fangs jutted, cruel and gleaming.

Nellon was fully recovered now. He followed the direction of Austin's gaze, and though his eyes saw the same thing, his mind pictured it in a different way.

Those ice teeth should have meant Big Tim's death. He, Nellon, had failed, had narrowly escaped losing his own life because of his blunder. Intent upon the shove which was to have sent Tim Austin hurtling to his death, he had forgotten the snow-concealed ice in the trail, as lethal with hidden treachery as a patch of quick-sand.

But he was still alive. They hadn't, as yet, even reached Ryska's hut, and Nellon knew another chance would present itself. He considered this with a curious mixture of impatience and reluctance.

"If it wasn't for Big Tim--" Nellon was hearing Laura say the words again, and once again the realms of unutterable bliss he read into them strengthened his resolve. One more chance--and this time he would not fail or waver.

"Brad--look!"

Vibrant with surprise and urgency, the words ripped aside the veil of Nellon's thoughts. His head jerked up.

Big Tim was on his feet. He was pointing up at the steep bank of the gorge down which they had tumbled.

Most of the disturbed snow had settled and the wind had carried away the rest. Nellon could see quite clearly.

There up on the bank, a small snow slide had taken place. And now, against the unbroken monotony of white, something gleamed in vivid contrast.

Nellon squinted. Gradually he began to make out details. The strange surface revealed by the slide seemed to have the mellow hue of bronze, but Nellon could not be sure, since it was queerly dappled and flecked with tones of gold and red. He thought it must be from the strain on his eyes, and closed them momentarily. But when he looked again the colors were as weird as he had last seen them. This time, however, he made out a detail which he had missed previously. The surface seemed to be crossed by a black line or stripe.

"Now what in the world can that be?" Tim Austin's voice was wondering, vaguely troubled. "It's like no sample of rock or soil we've taken. Metal--that's what it is!" he exclaimed of a sudden. "It's an exposed vein of some metal. Come on, Brad, let's have a look at it."

Nellon got to his feet, his eyes fixed upon that uncanny patch of something which stood out against the surrounding whiteness like a smear of blood.

Big Tim was already started up the bank. Nellon sucked in a breath and followed after him.

The climb was a hard and difficult one, and their recent physical jarring caused by the fall made it all the harder. But curiosity pulled them on like a vast magnet. In the exertion they forgot their aches and bruises. Slipping and sliding, clutching for handholds, floundering in loose drifts which filled pockets of hardened crust, they made their way slowly but surely up the bank.

Finally they stood before that strangely mottled patch of red and brown and gold. The mood of awed wonder which gripped them at once heightened and deepened.

"It is metal!" Tim Austin breathed. "But--but, Brad, it's not a vein. It's--"

"It's a door!" Nellon finished hoa.r.s.ely.

It was a door, a metal door in the snow covered bank of a falls that had, in some long, long ago, solidified to ice. A door to what? Where did it lead? What would be on the other side of it? What could be on the other side of a metal door on a world where it was doubtful that living beings had ever existed at all?

There was a rasp in Nellon's earphones. And then Big Tim Austin's voice followed it.

"Brad--I'm going in. This--why, this is the biggest find of the whole expedition!"

"It might be dangerous," Nellon pointed out, before he could become aware of the wealth of irony which lay behind the words. "We don't know what sort of life--"

"But this door has been hidden under snow for the Lord only knows how many years, Brad. Look where the crust had split here. It's thick, thick. Nothing has gone in or out for a h.e.l.l of a long time. If there were beings, they're either gone or dead."

And, as if having satisfied himself on this last account, Big Tim stepped directly up to the door. He was a tall man, yet he seemed dwarfed beside it. And it was obviously very ma.s.sive, for it was partly open and the width of the edge revealed could not have been spanned by the long, flexible metal fingers of their protecting gloves. The opening was a mere crack, as if someone had once made it so for a cautious glimpse of the world outside and never closed it again.

Big Tim placed his gloves against the projecting edge.

"Give me a hand, Brad. We'll see if we can open it further."

Together, they shoved. They drew upon ebbing reserves of strength, but what energy they managed to summon they threw into a brief, terrific effort to move the portal. But it did not move. Their combined strength seemed pitifully small against the weight they sought to budge.

They were about to relax their efforts in despair when, suddenly, transmitted from the metal of the door to that of their gloved hands, they felt what seemed to be a coughing whir. The sound smoothed out, deepened, and became a steady hum.

Startled, they leaped away. Their faces took on an intent, incredulous expression.

The door was opening. Slowly, majestically, it was swinging wide.

No force that they could see was behind it. The door seemed to move of its own volition. They stood as still as a pair of weird, metal statues, watching. Every sense, keyed to its highest, was directed at the widening gap.

At last all movement ceased, and the door hung wide. The humming note which had accompanied its opening dwindled to a whisper and died away. Revealed was a tunnel of utter blackness.

Tim Austin released his breath. The sound roused Nellon from the trance which gripped him.

"It's probably controlled by an automatic mechanism. When we shoved against it, we must have set that mechanism in motion."

"I'm going in, Brad," Big Tim said suddenly. "I'm going to see what's inside." He strode impulsively to the door. But at the threshold he stopped and turned and looked at Nellon.

Nellon smiled faintly and nodded. He strode after Big Tim. Together they entered the doorway.

Lights, built into the helmets of their suits, but up to this time unused, were turned on to illuminate the way. The tunnel, they saw, was a rectangular corridor or pa.s.sageway. It was lined with the same metal as that of the door.

At two intervals down the corridor they found it necessary to squeeze through half-opened doorways. The doors here were of the slide type and seemed to be controlled by machinery as was the one which they had opened to gain entrance to the corridor. But these could not be moved, nor did their efforts awaken any hum of machinery.

"You know," Big Tim remarked, "this arrangement of doors sort of reminds me of an airlock."

"I've noticed the same thing," Nellon responded. "But an airlock--" He shook his head, for this was one of the many things he couldn't understand.

Soon the corridor came to an end. Nellon and Austin found themselves in a small, square room, each side of which was lined with small gla.s.s cubicles or cabinets. In each reposed a transparent sphere with various inexplicable attachments and a compactly folded ma.s.s of some strange material.