could land her on Mars. Half the value of such a ship, unharmed and safe in port, would be a larger sum than he dared put in figures. And he must take her in, now that he had lost his own rocket!

He found the life-tubes, six of them, slender, silvery cylinders, lying secure in their niches, three along each side of the flier. None was missing. So the crew had not willingly deserted the ship.

He approached the main air-lock, at the center of the hull, behind the projecting dome of the bridge. It was closed. A glance at the dials told him there was full air pressure within it. It had, then, last been used to enter the rocket, not to leave it.

Thad opened the exhaust valve, let the air hiss from the chamber of the lock. The huge door swung open in response to his hand upon the wheel, and he entered the cylindrical chamber. In a moment the door was closed behind him, air was hissing into the lock again.

He started to open the face-plate of his helmet, longing for a breath of air that did not smell of sweat and stale tobacco smoke, as that in his suit always did, despite the best chemical purifiers. Then he hesitated. Perhaps some deadly gas, from the combustion chambers....

Thad opened the inner valve, and came upon the upper deck of the vessel. A floor ran the full length of the ship, broken with hatches and companionways that gave to the rocket rooms, cargo holds, and quarters for crew and passengers below. There was an enclosed ladder that led to bridge and navigating room in the dome above. The hull formed an arched roof over it.

The deck was deserted, lit only by three dim blue globes, hanging from the curved roof. All seemed in order—the fire-fighting equipment hanging on the walls, and the huge metal patches and welding equipment for repairing breaks in the hull. Everything was clean, bright with polish or new paint.

And all was very still. The silence held a vague, brooding threat that frightened Thad, made him wish for a moment that he was back upon his rugged ball of metal. But he banished his fear, and strode down the deck.

Midway of it he found a dark stain upon the clean metal. The black of long-dried blood. A few tattered scraps of cloth beside it. No more than bloody rags. And a heavy meat cleaver, half hidden beneath a bit of darkened fabric.

Mute record of tragedy! Thad strove to read it. Had a man fought here and been killed? It must have been a struggle of peculiar violence, to judge by the dark spattered stains, and the indescribable condition of the remnants of clothing. But what had he fought? Another man, or some thing? And what had become of victor and vanquished?

He walked on down the deck.

The torturing silence was broken by the abrupt patter of quick little footsteps behind him. He turned quickly, nervously, with a hand going instinctively to his welding arc, which, he knew, would make a fairly effective weapon.

It was merely a dog. A little dog, yellow, nondescript, pathetically delighted. With a sharp, eager bark, it leaped up at Thad, pawing at his armor and licking it, standing on its hind legs and reaching toward the visor of his helmet.

It was very thin, as if from long starvation. Both ears were ragged and bloody, and there was a long, unhealed scratch across the shoulder, somewhat inflamed, but not a serious wound.

The bright, eager eyes were alight with joy. But Thad thought he saw fear in them. And even through the stiff fabric of the Osprey suit, he felt that the dog was trembling.

Suddenly, with a low whine, it shrank close to his side. And another sound reached Thad's ears.

A cry, weird and harrowing beyond telling. A scream so thin and so high that it roughened his skin, so keenly shrill that it tortured his nerves; a sound of that peculiar frequency that is more agonizing than any bodily pain.

When silence came again, Thad was standing with his back against the wall, the welding arc in his hand. His face was cold with sweat, and a queer chill prickled up and down his spine. The yellow dog crouched whimpering against his legs.

Ominous, threatening stillness filled the ship again, disturbed only by the whimpers and frightened growls of the dog. Trying to calm his overwrought nerves, Thad listened—strained his ears. He could hear nothing. And he had no idea from which direction the terrifying sound had come.

A strange cry. Thad knew it had been born in no human throat. Nor in the throat of any animal he knew. It had carried an alien note that overcame him with instinctive fear and horror. What had voiced it? Was the ship haunted by some dread entity?

For many minutes Thad stood upon the deck, waiting, tensely grasping the welding tool. But the nerve-shattering scream did not come again. Nor any other sound. The yellow dog seemed half to forget its fear. It leaped up at his face again, with another short little bark.

The air must be good, he thought, if the dog could live in it.

He unscrewed the face-plate of his helmet, and lifted it. The air that struck his face was cool and clean. He breathed deeply, gratefully. And at first he did not notice the strange odor upon it: a curious, unpleasant scent, earthly, almost fetid, unfamiliar.

The dog kept leaping up, whining.

"Hungry, boy?" Thad whispered.

He fumbled in the bulky inside pockets of his suit, found a slab of concentrated food, and tossed it out through the opened panel. The dog sprang upon it, wolfed it eagerly, and came back to his side.

Thad set at once about exploring the ship.

First he ascended the ladder to the bridge. A metal dome covered it, studded with transparent ports. Charts and instruments were in order. And the room was vacant, heavy with the fatal silence of the ship.

Thad had no expert's knowledge of the flier's mechanism. But he had studied interplanetary navigation, to qualify for his license to carry masses of metal under rocket power through the space lanes and into planetary atmospheres. He was sure he could manage the ship if its mechanism were in good order, though he was uncertain of his ability to make any considerable repairs.

To his relief, a scrutiny of the dials revealed nothing wrong.

He started the gyro motors, got the great wheels to spinning, and thus stopped the slow, end-over-end turning of the flier. Then he went to the rocket controls, warmed three of the tubes, and set them to firing. The vessel answered readily to her helm. In a few minutes he had the red fleck of Mars over the bow.

"Yes, I can run her, all right," he announced to the dog, which had followed him up the steps, keeping close to his feet. "Don't worry, old boy. We'll be eating a juicy beefsteak together, in a week. At Comet's place in Helion, down by the canal. Not much style—but the eats!

"And now we're going to do a little detective work, and find out what made that disagreeable noise. And what happened to all your fellow-astronauts. Better find out, before it happens to us!"

He shut off the rockets, and climbed down from the bridge again.

When Thad started down the companionway to the officers' quarters, in the central one of the five main compartments of the ship, the dog kept close to his legs, growling, trembling, hackles lifted. Sensing the animal's terror, pitying it for the naked fear in its eyes, Thad wondered what dramas of horror it might have seen.

The cabins of the navigator, calculator, chief technician, and first officer were empty, and forbidding with the ominous silence of the ship. They were neatly in order, and the berths had been made since they were used. But there was a large bloodstain, black and circular, on the floor of the calculator's room.

The captain's cabin held evidence of a violent struggle. The door had been broken in. Its fragments, with pieces of broken furniture, books, covers from the berth,