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.