Then at last even their dim, animal intelligence saw that this was a losing battle. A cry rose and was shuttled from mouth to mouth. The silvery figures, now gray in ever-gathering dusk, wisped away from the cave-mouth. "Licked 'em!" cried Hannigan. "They're running, by Peter! Golly, Greg! Look at that pile out there!" There was awe in his voice, distaste in Greg's eyes as he looked on the motionless mound heaped before the cave. But Greg said, "Don't get rash! They may be planning a new attack. Breadon--what's wrong with you, man?" Ralph Breadon grinned wryly. "Fortune's favored child, that's me! They didn't have any weapons to shoot me with, so I shot myself. Bounced a bullet off the grill. It came back and pinked my arm." "Go get it dressed. There it comes!" cried Greg. "The new attack?" Sparks whirled. "The darkness. And the snow!" He was right. The threatened period of darkness had descended at last. Once again Titan was within the shadow of its primary. And once again the vast winds were keening from the hilltops, the great flakes of snow were tumbling from a lifeless sky. Greg's voice was exultant. "Now we're safe! In an hour or so we'll be behind a fortress of ice. And I don't think they'll lay siege to us in a blizzard for a solid week." His triumph was short-lived. For even as he anticipated victory, disaster beat on the portals of their refuge. From the depths of the cave came a shrill scream, the shout of Marberry, and Tommy's frantic cry-- "Greg! Come a-running! They've found the back entrance!" * * * * * The back entrance! Greg's heart lurched. He cursed himself, suddenly, for having tried to accomplish too much in making their cavern habitable. For by so doing, he had rendered them vulnerable in a spot where there would be no barrier of ice an hour hence. The back entrance. The archway they had broken out between their large cave and the smaller one wherein Tommy's livestock was herded. Somehow the Titanians had found the other cave, rolled away the boulders, and were now attempting to get at their quarry from the rear. Greg shouted, "Andrews, you stand guard here! One man will be enough. The rest of you--come on!" The first of the Titanians was pushing through the cleft just as he reached the main chamber. There was a look of unholy glee on the man-like creature's thin lips as he attained the cave. But it died there, suddenly, frostily. It was not Greg who dropped him. It was young Tommy, staggering under the recoil of a rifle almost as tall as himself, firing pointblank, bouncing back to reload manfully, bawling with youthful glee, "Got him, Greg!" * * * * *