"And the system of caverns--how far does it extend? Aren't those hills practically honeycombed their entire length? We might find--" "Wait!" The word came explosively, as her mind darted into the past, down the corridor of years. "Yes, I remember ... some of the caverns did lead out to this side, and father sealed them to make the Base airtight...." She gazed at the distant hills as if trying to recapture a forgotten scene. And a bulky shape hurtled forward, clawing for the weapons at her waist. But Carston had been watching. He thrust out a metal-shod foot and the convict went sprawling ludicrously into the swirling white dust. "Thank you, again!" the Commander said in a whisper. "This trip has been a revelation--in so many ways." Her face was as white as the powdery soil underfoot, and she was near collapse; but from some unknown source she still drew from enough strength reserve to maintain her authority. Hands on her atom-blast guns, she faced the men. "Into line as before. We've got to make the hills in less than one hour. Leave the sleds. It's the hills or your lives!" The effect was miraculous. Suddenly they were docile, grasping at the slender hope she offered them and content to have her bear the burden. Quickly they fell into line, with Vulc leading the way again. The men needed no urging; the knowledge that they only had one more hour of oxygen was enough. * * * * * If their trek up to now had been a nightmare, this latter stage surpassed even the most secret refinements of a Martian torture-chamber. In an agony of slowness the minutes lengthened and seemed to stand still. The low range of hills seemed to dance mockingly and recede into the distance beyond the horizon's endless rim. In addition now to the heat in their brains and the glare in their eyes, their lungs were tortured as they regulated the oxygen intake-valves to the barest minimum. After an eternity in which even memory seemed to have fled, they were walking on rock and the heat began imperceptibly to abate. Directly before them, the hills rose out of the torturing blaze. Cries that were little more than miserable croakings echoed through the radio-phones as the men broke ranks; they staggered on, holding to each other for support. Mark looked around for the Commander, and saw her clutching at Carston's shoulder for support, while his arm was about her waist, half-holding her up. The girl disengaged herself and by sheer will-power drove toward the base of the low-lying cliffs before them. "Wait!" she ordered. She stopped, and the men halted behind her, weaving on their feet. She stared around us as if desperately trying to recall something deeply imbedded in the matrix of the past; then she veered to the right, waving for Vulc and the men to follow. Mark tested his oxygen tank and glanced at the dial again. It read "ten minutes." It was a race with time which now, perversely, seemed to be rushing by on flying feet.