The expeditions had accumulated enough evidence from the desert to prove conclusively that the Martians had been a highly civilized and advanced people; more advanced, probably, than Earth. There were ruins of great cities in the south of the planet that must have been there for over two million years. The Martians had built well. As to what had happened to them--that was a mystery that remained unsolved. There had been no evidence of warfare of any sort, and a few rare translations of even rarer books, indicated that the Martians had eliminated diseases and had, in their time, colonized the entire solar system with their people. But now there was only the weeping wind and the barren sand--nothing more. He reached the door, twisted the handle on it. Having suspected that someone was inside, Lawrence was not surprised when it came open easily with a sharp creaking sound. It had been recently used, of course, since otherwise the years would have rusted it to the extent that the first man to open it again would have had to exert a great deal of strength. It was monometal, but everything except lead and a few beryllium alloys rusted in the Martian air. He took a torch from his utility bag, and the soft but brilliant green of the portable Howard-Brazier fluorescent stabbed into the darkness and tore away the shadows. There was nothing in the path of the beam that he could see. Only the red dust on the wings of the restless wind. He went in. The door creaked shut behind him. A tiny air purifier made sighings somewhere like a big dog with asthma. There was a bare metal table. And that was all. A door led into another room. He walked into it. Silence, save for the moan of the deathless wind, crying outside. It was dark in the room, with only the light of Deimos and Phobos shining into the glassite windows. He could just make out the darkness-shrouded bulks of shattered machinery in the corner. He pressed the button on his torch and the darkness fled in panic from the brightness of the light. The whisper in his brain came then. "_Don't_...." * * * * * His flashlight clattered to the metal floor, and his hand was on his blaster. Then he cursed himself for a fool and retrieved his torch. He did not, however, turn it on again. To be startled like that by mental telepathy was childish. It was something that every member of the Space Patrol had to master, and was an ability fairly common among intelligent people--many of whom practiced the art as something of a hobby. The only element of surprise was the fact that it was a strain on any ordinary man to project his thoughts that way, and speech was preferable when practicable. Still, there was no reason why anyone should not use telepathy if he wished. "Who--" he began aloud, then shrugged and concentrated on thinking: "Who are you?" "Speak aloud," came the thought. "It is easier for you, and makes your mental impulses clearer."