Two thousand feet below, Jim Holcomb, dizzy and gasping, manipulated the controls frenziedly, his eyes fastened on the dropping pressure-gauge. From somewhere outside the tent a dull thud sounded. "Crashed! Darl's crashed! It's all over!" Hope gone, only the instinct of duty held him to his post. But the gauge needle quivered, ceased its steady fall and began a slow rise. Jim stared uncomprehendingly at the dial, then, as the fact seeped in, staggered to the entrance. "That's better, a lot better," he exclaimed. "But, damn it, what was that crash?" * * * * * The headquarters tent was at one edge of the circular plain. Jim's bleary eyes followed the springing arch of a vertical girder, up and up, to where it curved inward to the space ship landing lock that hung suspended from the center of the vaulted roof. Within that bulge, at the very apex, was the little conning-tower, with its peri-telescope, its arsenal of ray-guns and its huge beam-thrower that was the Dome's only means of defense against an attack from space. Jim's gaze flickered down again, wandered across the brown plain, past the long rows of canvas barracks and the derrick-like shaft-head. Hard by the further wall a crumpled white heap lay huddled. "My God! It was his plane!" The burly Earthman sobbed as his ten-foot leaps carried him toward the wreck. Darl was his friend as well as Chief, and together they had served the Interplanetary Trading Association, ITA, for years, working and fighting together in the wilds of the outer worlds. A thought struck him, even as he ran. "What in th' name o' Jupiter's nine moons stopped th' leak?" He glanced up, halted, his mouth open in amazement. "Well, I'm a four-tailed, horn-headed Plutonian if there ain't th' boy himself!" Far up in the interlaced steel of the framework, so high that to his staring comrade he seemed a naked doll, Darl stood outstretched on a level beam, his tiny arms holding a minute square against the wall. Lucky it was that he was so tall and his arms so long. For the saving plate just lapped the upper rim of the hole, and stemmed the fierce current by only a half-inch margin. * * * * * The throbbing atmosphere machine in the sub-surface engine-room was replacing the lost air rapidly, and now the increasing pressure was strong enough to hold the translucent sheet against the wall by its own force. Jim saw the extended arms drop away. The manikin waved down to him, then turned to the shell again, as if to examine the emergency repair. For a moment Darl stood thus, then he was running along the girder, was climbing, ape-like, along a latticed beam that curved up and in, to swing down and merge with the bulge of the air-lock's wall. "Like a bloomin' monkey! Can't he wait till I get him down with th' spare plane?"