"Nothing," Torcred managed to get out. "The shadows play tricks...." As they crossed the rise, Torcred halted to tie a bootlace that didn't need tying. There were no tracks in the soft sand. Torcred remembered fearfully what he had heard of the visions that heralded death by thirst--but even sane people saw things that weren't there, such as the phantom lakes that had mocked them in the midday heat. But he had been sure that vision was looking at him.... Two or three miles further on, it was almost dark. Torcred sank wearily down in the lee of a high ridge. "We'd better stop here. Perhaps a night's sleep will give us strength." The girl sighed. "I think we will die on this desert, terrapin." Torcred felt a stirring of the anger her use of that word always roused in him. But he said only, "We've covered perhaps a third of the way. Two more days, then." He remembered that pebbles in the mouth ease thirst; they tried that, and it helped a little. Then they scooped hollows in the sand for sleep. Ladna wriggled out of the heavy flying suit that, stickily uncomfortable as it was, had protected her from the sun. The sleeveless shirt and shorts she wore beneath clung damply to her; even through a haze of exhaustion Torcred was stirred by the sight of her slender body, her mildly rounded breasts and long straight legs.... He slept like a log, and woke in the dim pearly light before dawn, still tired, his mouth like a furnace. * * * * * It was a moment before he realized that the bird-girl's piercing whisper had wakened him, and sat up abruptly. Spots danced before his eyes; he felt her hand tighten in warning on his arm. Then he saw by that ghostly light, not a hundred yards away, a thing of nightmare. It was a huge gray monster of metal, a moving fortress going steadily forward on endless treads that hardly dented the soft sand beneath it, though it must have weighed half a hundred tons. Shod with silicone-rubber, it rolled in an unreal silence, the purr of its engine scarcely audible in the early hush, past the two frightened watchers under the dune, and vanished over another crest. The girl still clutched Torcred's arm, finding perhaps some flimsy reassurance in the resilient hardness of his tensed muscles. "What was it?" she gasped. "That was a panzer," Torcred informed her in a low voice. "A big relative of the terrapins, that prowls the desert alone, by night. It carries a crew of three to six, can see in the dark and move without a sound. It's one of the most formidable land machines in the world." Ladna drew a shuddering breath. "I hope it doesn't come back." "Don't worry. I told you it was nocturnal--at this hour it's hunting a good safe spot to lie up for the day." The girl was wearily pulling on her coveralls; her fire-blue eyes were clouded with hopelessness as they gazed into the gray dawn. "Perhaps it would have been better if it had seen us--better than what's ahead of us."