"No, nor the demons either. It was the hand of man struck him down, my boy. If it's violent death you're trying to explain, don't drag in the supernatural. There's enough murder in the hearts of humankind to take care of every case." In the third room Green said, "There's no wall of dust to stop us. The ionic charges haven't stopped working. Notice how clean everything is. Ah, here we are! Before the door!" Grizquetr looked puzzled. "Door? I see only a blank wall." "That's all I saw too," said Green, "and that is all I would ever have seen, if it hadn't been for the tale of Samdroo." "Let me tell you how you got in!" chattered the boy excitedly. "I know what you were thinking of, what you did. You stood before the wall and you made a sign like this on it!"--He traced a rough outline of a rocket against the cool white metal--"and the wall suddenly slid to one side, and you had an entrance. See!" A whole section had moved noiselessly into the wall, leaving a round doorway. "Yes, I remembered the story of Samdroo and, though it was ridiculous to think that it would work, I did what the Sailor did. Remember that the cannibals were after him, and he ran into the cave and came to just such a blank wall. And he, wishing to protect himself against the evil spirits that he was sure lived in the cave, traced the sign that is supposed to prevent them from touching a man. And the door slid open and he plunged on into the chambers of the wicked magician, the savages howling frustratedly after him. "And," continued Green, "I did just what he did, and the sign proved to be an _Open, O Sesame_ for me." "A what?" "Never mind. The point is that the ancient maintenance men must have used just such a gesture to open the door, or else used it in conjunction with other means. And if they did, then they must also have been repair technicians for the ships that landed here. Perhaps the sign of the rocket was a secret symbol for their guild. I don't know, but it sounds reasonable." Ignoring the boy's flood of questions, he walked into a great room. It was more bare than he'd expected when he had found it the first time; it contained four machines or their fuel supplies, all concealed in four large square metal containers. In the center of the room was a chair and an instrument panel. The panel contained six TV windows, several oscilloscopes, and dials whose purpose he didn't know. But the controls attached to the arms of the chair seemed simple enough. "The only trouble," he said, "is that I don't know where the activating switch is. I tried to find it the other night and couldn't. Yet, it must be so obvious that I'll feel like a fool when I do locate it." Vainly he pulled at the little levers set in the arms.