"A map," he said amusedly. "He's pointed out his own city and a couple of others, and he wants us to tell him where we come from. Evelyn--er--how are we going to explain a trip through five dimensions in a sketch?" Evelyn shook her head. But a shadow passed over their heads. The pilot leaped to his feet and shouted. There were three planes soaring above them, and the pilot in the first was in the act of releasing a smoking object over the side. At the grounded pilot's shout, he flung his ship into a frantic dive, while behind him the smoking thing billowed out a thicker and thicker cloud. His plane was nearly hidden by the vapor when he released it. It fell two hundred yards and more away, and the white mist spread and spread. But it fell short of the little hillock. * * * * * "Quick thinking," said Tommy coolly. "He thought we had this man a prisoner, and he'd be better off dead. But--" Their captive was shouting again. His head thrown back, he called sentence after sentence aloft while the three ships soared back and forth above their heads, soundless as bats. One of the three rose steeply and soared away toward the city. Their captive, grinning, turned and nodded his head satisfiedly. Then he sat down to wait. Twenty minutes later a monstrous machine with ungainly flapping wings came heavily over the swamp. It checked and settled with a terrific flapping and an even more terrific din. Half a dozen armed men waited warily for the three to approach. The golden weapons lifted alertly as they drew near. The wounded man explained at some length. His explanation was dismissed brusquely. A man advanced and held out his hands for Tommy's weapons. "I don't like it," growled Tommy, "but we've got to think of Earth. If you get a chance hide your gun, Evelyn." He pushed on the safety catches and passed over his guns. The pilot he had shot down led them onto the fenced-in deck of the monstrous ornithopter. Machinery roared. The wings began to beat. They were nearly invisible from the speed of their flapping when the ship lifted vertically from the ground. It rose straight up for fifty feet, the motion of the wings changed subtly, and it swept forward.