Men were tossing sections of lattice duckboard out upon the swamp, extending a narrow walkway toward Four's airlock, and within a few minutes the new arrivals were scrambling down. Barry paid little attention to the noisy greetings and excited talk. Impatiently he trotted toward the rock ledge, searching for one particular figure among the men and women who waited. "Dorothy!" he said fervently. Then his arms were around her and she was responding to his kiss. Then unexpected pain tore at his chest. Her lovely face took on an expression of fright even as it wavered and grew dim. The last thing he saw was Robson Hind looming beside her. By the glow of an overhead tubelight he recognized the kindly, deeply lined features of the man bending over him. Dr. Carl Jensen, specialist in tropical diseases. He tried to sit up but the doctor laid a restraining hand on his shoulder. "Water!" Barry croaked. The doctor held out a glass. Then his eyes widened incredulously as his patient deliberately drew in a breath while drinking, sucking water directly into his lungs. "Doctor," he asked, keeping his voice low to spare his throat. "What are my chances? On the level." Dr. Jensen shook his head thoughtfully. "There's not a thing--not a damned solitary thing--I can do. It's something new to medical science." Barry lay still. "Your body is undergoing certain radical changes," the doctor continued, "and you know as much--more about your condition than I do. If a normal person who took water into his lungs that way didn't die of a coughing spasm, congestive pneumonia would get him sure. But it seems to give you relief." Barry scratched his neck, where a thickened, darkening patch on each side itched infuriatingly. "What are these changes?" he asked. "What's this?" "Those things seem to be--" the doctor began hesitantly. "Damn it, I know it sounds crazy but they're rudimentary gills." Barry accepted the outrageous statement unemotionally. He was beyond shock. "But there must be--" Pain struck again, so intense his body twisted and arched involuntarily. Then the prick of a needle brought merciful oblivion. II Barry's mind was working furiously. The changes the Sigma radiations had inflicted upon his body might reverse themselves spontaneously, Dr. Jensen had mentioned during a second visit--but for that to happen he must remain alive. That meant easing all possible strains. When the doctor came in again Barry asked him to find Nick Podtiaguine. Within a few minutes the mechanic appeared. "Cheez, it's good to see you, Barry," he began. "Stuff it," the sick man interrupted. "I want favors. Can do?" Nick nodded vigorously. "First cut that air conditioner and get the window open." Nick stared as though he were demented, but obeyed, unbolting the heavy plastic window panel and lifting it aside. He made a face at the damp, malodorous Venusian air but to Barry it brought relief.