"It was the right thing to do, the level-headed thing," Corriston said. "You couldn't have used better judgment." "Then it's all right if I go back with you?" Corriston shook his head. "No, Freddy. I'd rather you didn't. Don't you understand? You've done _more_ than your share. Now it's my turn." Freddy tightened his lips and stared for a moment at the glitter of sunlight on the caterpillar tread of the nearest tractor. Finally he said, "All right, Lieutenant Corriston. If it's an order." "It's an order, Freddy." Corriston gave Freddy's shoulder a pat. Then, after the briefest pause, he said: "There's no substitute for the kind of fast-thinking resourcefulness you've just displayed, Freddy. In a dozen years you'll be heading an expedition and it won't be the kind that gets bogged down after the first thousand miles. You can take my word for that." He turned then and walked toward the ship. In a moment he had passed the ship and was moving out into the desert beyond, and Freddy wondered how a man could remain so calm in an affair of life and death such as this. It was just as well, perhaps, that he could not see Corriston's face as he moved still further away from the ship into a loneliness of desert and sky. * * * * * She was lying in a wind-scoured hollow beneath a seventy-foot dune, her head resting on one sharply-bent elbow, a look of utter exhaustion on her face. Her eyes were closed, and even from where he stood Corriston could see that she was breathing heavily. He could see the slight rise and fall of her bosom, the trembling vibration of her oxygen mask. She was completely alone. He stood for an instant absolutely motionless on the summit of the dune, staring down at her, noticing in alarm the hollow contour of her cheeks on both sides of the oxygen mask, and the slight tinge of gray that had crept into her countenance. Then he started downward. Almost instantly the sand rose like an unsteady sea on all sides of him, and a warning signal sounded in his brain. He could connect it with no cause. Beneath him stretched only the wind-scoured inner surface of the dune, dazzling his eyes with its brightness, mirroring the sunlight like a burning glass. For a moment the brightness deceived him, and he did not realize that there were shadowed hollows directly beneath him, dark fissures in the tumbled sand wide enough to conceal a crouching man. He did not even see the shadow creeping toward him over the sand. Only the dazzle for an instant and the gleam of sunlight on Helen Ramsey's tousled hair. Then, suddenly, he was aware of the danger, fully awake and aware. But realization came too late. Abruptly, without warning, a knife blade flashed in the sunlight and he felt an agonizing stab of pain just below his left kneecap.