But suddenly a distant rumbling sound was heard, increasing rapidly in volume. The floor of the cave vibrated; masses of rock dropped from the walls. The light of the volcano across the valley was suddenly obscured in an immense cloud of black smoke. The twilight within the cave was succeeded by almost impenetrable darkness. Shrieking in terror, the Drilgoes bolted, while Jim lay straining at his ropes, expecting each moment to be crushed by the masses of rock that were falling all about him. Suddenly a soft whisper came to Jim through the darkness: "Jim! Are you safe! Where are you? I can't see you! Speak to me!" It was Lucille's voice, and Jim called back, husky and tremulous in the sheer joy that had succeeded his anticipation of instant death. * * * * * Then he felt the girl kneeling at his side, and heard her hacking at his bonds. A whole minute passed before the stone knife was able to sever the last of the stout withes, however. Then Jim was swaying on his feet, and Lucille's arms were about him, and for a few moments their fears were forgotten in the renewal of their love. "I heard what that devil said to you last night," the girl said. "He means to kill you with awful tortures. He is away now, on some task or other, but he'll be back at any moment. We must get away at once--we three. Dad's in another cave not far away, and his guards bolted after the earthquake." The earth was still rumbling, and the cavern still vibrating, but it was clear that there was no time to lose. As soon as the quake subsided the Drilgoes would return. Guided by Lucille, Jim groped his way through the cavern. The girl called softly at intervals, and presently Jim heard old Parrish's answering call. Then the old man's form appeared in silhouette against the dark. "I've got Jim," Lucille whispered. "Are you ready, dad?" "Yes, yes, I'm ready," chattered the old man. "Now's our chance. I know a place where we can hide in the thick forests, where the Ray of the Atlanteans cannot penetrate the mists. Let's go! Let's go!" Gripping hands, the three started back toward the point where a faint patch of darkness showed out the entrance to the cavern. They were nearing it when another and more violent shock flung them upon their faces. Huge masses of rock came hurtling down from the roof and sides of the cavern, and again the three seemed to escape by a miracle. * * * * * Suddenly a huge shaft of fire shot from the crater opposite, evolving into an inverted cone that made the whole land dazzlingly bright. It pierced the mists in the valley underneath, and by that light Jim could see a great wave of lava streaming down the mountain sides, like soup spilled out of a bowl. A gush of black smoke followed, and the light went out.