The volcano, even in death, was ages old; its cold desolation showing plainly on the screen. No fires poured now from a hot throat; the molten sea that once had raged within had hardened and choked that vast throat with rock that had frozen to make one enormous plain. Ringed about by the jagged sides of the tremendous volcano, the floor within seemed smooth by comparison, except for another depression at its upper edge. Here was another and smaller crater inside the great ringed wall of Hercules. The light of the sun struck slantingly across to throw one side of the gigantic cup into shadow, while the opposite rim blared brightly in the lunar dawn. And within the smaller crater, too, one side was dead black with shadow. Dead!--No moving thing--no sign of life or indication that life might ever have been! A dead world, this!--its utter desolation struck Chet's half-uttered exclamation to a hoarse whisper of dismay. In all the universe what less likely place might one discover wherein to look for man? * * * * * His gaze was held in fascinated hopelessness on the barren, mountainous ring, on the inner inverted cone, on the shadow within that smaller crater--_on a tiny pinpoint of light that was flashing there!_... He hardly knew when he raised one trembling hand and pointed, while a voice quite unlike his own said huskily: "Look! Look! I told you it was so!... There! In that little crater!--it's signaling! Three dots--now three dashes--three dots again! The old S O S!--the old call for help! It's Haldgren!" Again the screen showed the smiling scientist. "Caught them just right," he said, "and glad to be of service. Now, if there's anything else I can do--" "Thanks!" said Chet in that same strained voice. "Thanks! There's nothing else." A switch clicked beneath his hand, and once more the screen was dark. "Those dots and dashes! The old S O S! Who could doubt now?" Chet was telling himself this when the Commander's voice broke in harshly. "Even you must see the absurdity of this, Bullard. You have heard this astronomer tell you what the rest of us knew for ourselves--that there is no air on the Moon; that it is impossible for a human being to live there. And you would have us believe that a man has lived there for five years! "But I am taking your distinguished record into account; I am overlooking your insubordination and the folly of your reasoning. Perhaps your feeling about Haldgren does you credit; but Haldgren is dead. Now I am giving you another chance: I order you to come forward and receive this honor, which is an honor to the entire Service of Air." * * * * * Chet was staring in open amazement. "No air on the Moon," this man had said. And what of that? Neither was there air in interplanetary space, yet he had traveled there. It was inconceivable that this imperious and dictatorial man could be so blind.