Parallel evolution on two inner planets of the same system? Somewhere, sometime, a common ancestor? Martin noted the shoulder-high doors, the heavier gravity, remembered the inhabitants of the city vanished before the thing that was to become man ever emerged from the slime, and he decided to grin at himself, at his own imagination. Rodney jerked his scarecrow length about quickly, and a chill sped up Martin's spine. "What's the matter?" The bony face was white, the gray eyes were wide. "I saw--I thought I saw--something--moving--" Anger rose in Martin. "You didn't," he said flatly, gripping the other's shoulder cruelly. "You couldn't have. Get hold of yourself, man!" Rodney stared. "The wind. Remember? There isn't any, here." "... How could there be? The buildings protect us now. It was blowing from the other direction." Rodney wrenched free of Martin's grip. He gestured wildly. "That--" "Martin!" Wass' voice came through the receivers in both their radios. "Martin, I can't get out!" * * * * * Rodney mumbled something, and Martin told him to shut up. Wass said, more quietly, "Remember that metal band? It's all clear now, and glittering, as far as I can see. I can't get across it; it's like a glass wall." "We're trapped, we're trapped, they are--" "Shut up, Rodney! Wass, I'm only two sections from the edge. I'll check here." Martin clapped a hand on Rodney's shoulder again, starting him moving, toward the city's edge, past the black, silent buildings. The glittering band was here, too, like a halo around a silhouette. "No go," Martin said to Wass. He bit at his lower lip. "I think it must be all around us." He was silent for a time, exploring the consequences of this. Then--"We'll meet you in the middle of the city, where we separated." Walking with Rodney, Martin heard Wass' voice, flat and metallic through the radio receiver against his ear. "What do you suppose caused this?" He shook his head angrily, saying, "Judging by reports of the rest of the planet, it must have been horribly radioactive at one time. All of it." "Man-made radiation, you mean." Martin grinned faintly. Wass, too, had an active imagination. "Well, alien-made, anyhow. Perhaps they had a war." Wass' voice sounded startled. "Anti-radiation screen?" Rodney interrupted, "There hasn't been enough radiation around here for hundreds of thousands of years to activate such a screen." Wass said coldly, "He's right, Martin." Martin crossed an intersection, Rodney slightly behind him. "You're both wrong," he said. "We landed here today." Rodney stopped in the middle of the metal street and stared down at Martin. "The wind--?" "Why not?" "That would explain why it stopped so suddenly, then." Rodney stood straighter. When he walked again, his steps were firmer. They reached the center of the city, ahead of the small, slight Wass, and stood watching him labor along the metal toward them.