His mirth was infectious. The engineers grinned and looked at each other and laughed a little. They hadn't the slightest notion of why Kortha laughed, or why they grinned, but no one could resist such a magnificent confidence in a city that was without a weapon, and yet a gun all by itself. * * * * * Kortha spread his hands, asking, "This is a radio-city, isn't it? It has every science necessary to perfect radio technique, hasn't it? Get me Xax! He and I have work to do." The tumblie shrilled a greeting, passing the engineers leaving the room. He rolled across to the bronzed giant, clicking his needles, eager, curious. Kortha grinned at him, dropped to a knee to speak to him. "You are the only one in all Ruuzol who can do this job, Xax. Any other who left here would be shot by the guards Guantra will post before he goes. It's up to you. Will you help me fight Guantra? I won't blame you if you refuse." "Tell me what you want me to do," said Xax simply. "You waste time, talking nonsense." Kortha took Xax to the tower window and showed him the red cliffs that rose all around Ruuzol, towering toward the sky. "Years ago, when I first came to Ruuzol from the Academy, I sank cables into the metal of those cliffs. I laid them underground to the mesa, here. I connected their vast bulk with the generators and tube relays of the city. I have to know if those cables are still attached. You can tell me. I shall let you know what tests to apply in the tiny caves where the cable-controls are sunk. You can perform those tests with you feelers, Xax." "What tests, Kortha?" The giant told him, repeating himself for emphasis. But the tumblie understood, and said so. Kortha watched him click-roll out of the tower, and rose, sighing. To Ilse he said, "Let's go back to the laboratories again. I'll need to make more diagrams. Get the engineers to meet me. They'll have to change cable terminals and install them on a different hookup." Down in the laboratories, Ilse sat for hours, watching Kortha as he labored over charts and graphs, often without moving more than hands and eyes for an hour at a stretch. When he was done, he stood up and stretched like a waking tiger. He grinned, and handed the graphs to her. Her eyes widened, looking down. "Why, this is just--" she looked up, startled, beginning to smile. "Something any modern housewife knows," he agreed. He laughed and said, "Guantra will call it more magic." "It is magic," Ilse said softly. "It is the magic of your brain that can think of something like this at a time like this." "Bah," chuckled Kortha, but he tingled meeting her eyes. Hours later, the western sky grew dark with warships. Kortha and Ilse stood once more in the tower over the paraboloid city, their arms touching. Before Kortha lay a white metal box with a red enamel switch disappearing inside it.