Thirty yards further, the cliffs curved in sharply. Rounding it, the Commander gave a glad cry. In the center was a gigantic metal door, hermetically sealing what had once been the entrance to a cave. The men staggered forward, some of them clawing feebly at the barrier. Others sank wordlessly to the rocky ground. They weren't even sure that beyond that metal wall they would find life-giving air. The Commander had drawn both atom-pistols, and stood there surveying the barrier as if paralyzed. "What are you waiting for?" Mark pressed forward. "In minutes, the men will be dying! Blast an opening!" For the very first time, Mark saw her hesitant, indecisive, as if unable to think. "But the air ..." she managed to gasp. "It will escape from the caves, clear back to the Base! All those men there ... and father ... their lives are more important than ours!" * * * * * In those brief seconds Mark admired her. Despite the deadly threat to the Earth she embodied, he admired her for her humanity and loyalty to the men at the Base. But there was no time to lose. He made her decision superfluous. "We've got to chance it!" With a swift, darting movement he wrested an atom-blast gun from her hand and discharged it steadily at the metal door, at a point just above the ground. A second later she was helping him with the other gun. Instantly the metal turned fiery red, then white, and finally a circular section fell outward with a hissing rush of air. "Dive in, men!" With the dregs of a strength he didn't know he still possessed, Mark grasped the men and pushed them toward the aperture, helped shove them through. "Throw your helmets back!" he shouted. "In you go," he told the Commander, and despite her protests he lifted her off her feet, almost handing her through the blasted entrance. Only Vulc and Mark were left. As the Earthman crawled through, he motioned for Vulc to follow. The metallic being dropped to all fours and pushed in his arms, his head, his massive shoulders. His sides scraped the still hot edges of the aperture. And there he stuck. The men inside grasped his arms and pulled, but in vain. Vulc gazed ludicrously from side to side and heaved prodigiously, but in vain. The Vulcanian seemed molded to the hole. "Wait! Tell him not to struggle, not to move!" Mark was exultant as he turned to the girl. "The air's no longer rushing away; if he'll only remain there until we can get back with equipment to seal that hole, the danger's over!" Vulc seemed to be pondering; his limbs sprawled like a distorted swastika, and on his usually blank, fluid face was something like surprise. In the dim recesses of his alien mind he could find no parallel to this.