Troy chewed his lip anxiously, the moisture-conserving suits they wore for outside duty on Cassa One, which concealed the two sets of swim flippers along their sides and left the top pair of upper limbs ... short, sturdy brown arms with hands larger than human hands, quite as capable and rather unpleasantly human in appearance ... free for use. The transparent, inverted-triangle helmets were clamped down. As he looked on, one of their big atmospheric personnel carriers came gliding into sight behind the immobile ranks. There were commands, and the Tareegs turned and filed into the vehicle, moving with the rapid, awkward little waddle which was their method of progress on land. A minute or two later, the loaded carrier moved out of the hangar, and the lights in the vast structure slowly faded away. * * * * * Where were they going? They were carrying the usual weapons, but this was not some dryland drill. Troy could not remember seeing so large a group leave the station before. The uneasy conviction returned that the move must be connected with the fact that clouds had begun to show in Cassa One's skies, that the mile-thick boulders of ice which had been brought across space already were falling through the atmosphere of the desiccated world. One or two more undisturbed days, Troy thought. In that time it would become clear whether Newland was going to recover sufficiently to be able to play a part in his plans. Only two sections of the shattered courier ship, the inertial shielding and the autonav, had been needed to transform the Hammerheads' interstellar drone twenty feet from the tunnel exit into a spaceship which men could ride and direct. Both those sections had been repairable, and everything else Troy had been able to steal or build in the station. Month after month passed as he brought it all together in the tunnel, familiarized himself with every necessary detail of the drones' mechanisms and fitted in the new installations ... first in theory, then in actual fact. A part of almost every night was spent in the darkened hangar, assembling, checking and testing one section or another, then disassembling everything and taking it back down into the tunnel before the moment came when the Tareeg watch-beams would sweep again through the hangar. The beam-search was repeated each three hours and twenty-seven minutes throughout the night. Within that period of time, Troy would have to carry out a final complete assembly, let the drone roar into life and send it flashing up through the force-screen and into space. By now, he knew he could do it. And if he had calculated the drone's capacity correctly, he would then be less than six months from Earth. The Hammerheads had nothing they could send after him.