Chance was with them this time. The first sand car they found still had the keys in the lock. It was battery-powered, but contained a full charge. Much quieter than the heavy atomic cars, it sped smoothly out of the city and across the sand. Ahead of them the sun sank in a red wave of color. It was six o'clock. By the time they reached the tower it was seven, and Brion's nerves felt as if they were writhing under his skin. Even though it looked like suicide, attacking the tower brought blessed relief. It was movement and action, and for moments at a time he forgot the bombs hanging over his head. The attack was nerve-rackingly anticlimactic. They used the main entrance, Ulv ranging soundlessly ahead. There was no one in sight. Once inside, they crept down towards the lower rooms where the radiation had been detected. Only gradually did they realize that the magter tower was completely empty. "Everyone gone," Ulv grunted, sniffing the air in every room that they passed. "Many magter were here earlier, but they are gone now." "Do they often desert their towers?" Brion asked. "Never. I have never heard of it happening before. I can think of no reason why they should do a thing like this." "Well, I can," Brion told him. "They would leave their home if they took something with them of greater value. The bombs. If the bombs were hidden here, they might move them after the attack." Sudden fear hit him. "Or they might move them because it is time to take them--to the launcher! Let's get out of here, the quickest way we can." "I smell air from outside," Ulv said, "coming from down there. This cannot be, because the magter have no entrances this low in their towers." "We blasted one in earlier--that could be it. Can you find it?" Moonlight shone ahead as they turned an angle of the corridor, and stars were visible through the gaping opening in the wall. "It looks bigger than it was," Brion said, "as if the magter had enlarged it." He looked through and saw the tracks on the sand outside. "As if they had enlarged it to bring something bulky up from below--and carried it away in whatever made those tracks!" Using the opening themselves, they ran back to the sand car. Brion ground it fiercely around and turned the headlights on the tracks. There were the marks of a sand car's treads, half obscured by thin, unmarked wheel tracks. He turned off the lights and forced himself to move slowly and to do an accurate job. A quick glimpse at his watch showed him there were four hours left to go. The moonlight was bright enough to illuminate the tracks. Driving with one hand, he turned on the radio transmitter, already set for Krafft's wave length. When the operator acknowledged his signal Brion reported what they had discovered and his conclusions. "Get that message to Commander Krafft now. I can't wait to talk to him--I'm following the tracks." He killed the transmission and stamped on the accelerator. The sand car churned and bounced down the track.