"I don't know what killed it," Thompson said. Before landing they had circled this world. From the air they had seen more than a dozen cities such as this one. All of them dead, all of them deserted, all of them with streets overgrown by shrubbery, the pavements buckling from the simple pressure of roots pushing upward, the buildings falling away into ruin for the same reason. But they had seen no inhabitants. They had seen the roads the inhabitants had built to connect their cities, deserted now. They had seen the fields where these people had once worked, fields that now were turning back into forests. They had seen no evidence of landing fields for air craft or space ships. The race that had built the cities had not yet learned the secret of wings. From the roof of the building where they stood, the only living creatures to be seen were visible through the plastic viewport of the ship below them--Grant, the communication specialist, and Buster, the ship's cat. Grant had been left to guard the vessel. Buster had been required to remain within the ship, obviously against his will. He had wanted to come with Thompson. A trace of a grin came to Thompson's face at the sight of the cat. He and Buster were firm mutual friends. "I don't like this place," Kurkil spoke suddenly. "We shouldn't have landed here." Kurkil paused, then his voice came again, stronger now, and with overtones of fear in it. "There's death here." He slapped at his arm, stared around him. "What happened?" "Something bit me." He showed the back of his hand. A tiny puncture was visible. "Some insect," Thompson said. The matter of an insect bite was of no concern. Kurkil, and every other member of this expedition, were disease-proof. Back in Sol Cluster vaccines and immunizing agents had been developed against every known or conceivable form of germ or virus. Each member of the crew had been carefully immunized. In addition, they had been proofed against stress, against mounting neural pressure resulting from facing real or imaginary danger. Barring space collision or an accident on a world they were exploring, nothing could happen to them. "We checked the air, took soil and vegetation samples, before we landed," Thompson said. "There is nothing here that is harmful to a human." There was comfort in the thought. Kurkil brightened perceptibly. "But, what happened to the race that built this city?"