He asked himself a score of times if his impulsive, desperate act had not been a horrible mistake. And he found the same answer always: it was all he could have done. Had he attacked Schwartzmann he would have been killed--and Walt, too! Schwartzmann would have had Diane. Only some such stupefying shock as the effect of the shattered control could have checked Schwartzmann. No, there had been no alternative. And the thing was done. Finally, irrevocably done! * * * * * Chet walked to the cave-mouth to stare down at the ship below him in the valley. From the fumerole's throat came a steady, rolling cloud of shimmering green; the ship was immersed in it. The voice of Herr Kreiss spoke to him; the scientist, too, had come forward for another look. "If it were at the bottom of the sea," he said, "it would be no more inaccessible. It is, in very fact, at the bottom of a sea--a sea of gas. We could penetrate an aqueous medium more easily." "And," Chet pondered slowly, "if only I could have returned.... With time--and metal bars--and tools that I could improvise--I might...." His voice trailed off. What use now to speculate on what he might have done. The scientist concluded his thought: "You might have reconstructed the control--yes, I, too, had thought of that. But now, the gas! No--we must put that out of our minds, unless we would become insane." Chet turned back into the black and odorous cave. He saw Harkness who was flexing a bow he was making for Diane; he was showing her how to grip it and let the arrow run free. "Towahg was the last one I instructed," Walt was saying; and Chet knew from the deep lines in his face that his attempt at casual talk was for Diane's benefit; "I wonder how long Towahg remembered. He was a grateful little animal." "Towahg?" queried Kreiss. "Who is Towahg?" "Ape-man," Harkness told him. "Friendly little rascal; he helped us out when we were here before. He saved Diane's life, no question about that. I showed him the use of the bow; jumped him ahead a hundred generations in the art of self-defense." "And offense!" was Kreiss' comment. "There are certain drawbacks to arming a potential enemy." "Oh, Towahg is all right," Harkness reassured the scientist, "although he may have taught the trick to others of the tribe who are not so friendly." "Where are they? In what direction do they live?" Kreiss continued. "Want to make a social call?" Chet inquired. "You needn't mind those little formalities up here, Doctor." * * * * * But in the mental makeup of Herr Doktor Kreiss had been included no trace of humor; he took Chet's remark at face value. And he answered in words that echoed Chet's real thoughts and that took the smile from his lips.