"We will rip the big web out with detonite," Harkness told the others when morning came. "But I want to get the spider, too." A touch upon the web with a stick brought an instant response. Again they saw in all its repulsiveness the thing that seemed a creature of some horrible dream. The eyes glared, while hairy feelers seized the web and shook it in furious rage. Harkness, fearing another discharge of the nauseating, viscous liquid, withdrew with the others far back in the cave. "Wait," he told them. "I have a plan." The creature vanished, and Harkness went cautiously forward to the web. He took a detonite cartridge from his belt and placed it on the floor close to the ropy strands. Another, and another, until he had a close-packed circle of the deadly things. Then he placed a heavy, metallic piece of rock beside them and proceeded, with infinite care, to build a tower. One irregular block upon another: it was like a child at play with his toys. Only now the play was filled with deadly menace. The stones swayed, then held in precarious, leaning uncertainty; the topmost was directly above the cartridges on the floor. "Back!" he ordered the others, "and lie flat on the floor. I must guess at the amount of explosive for the job." Chet and Diane were safe as Harkness weighed a fragment of metal in his hand. One throw--and he must not hit the tower he had built.... The rock struck into the network of cords; he saw it clinging where it struck, and saw the web shaking with the blow. Over his shoulder, as he ran, he glimpsed the onrush of the beast. Again the eyes were glaring, again the feelers were shaking furiously at the web. They touched the leaning stones! He had reached the place where Chet and Diane lay and saw the beginning of the tower's fall; and in the split second of its falling he threw himself across the body of the prostrate girl to shield her from flying fragments of stone. A blast of air tore at him; his ears were numbed with the thunder of the blast--a thunder that ended with a crashing of stone on stone.... * * * * * Slowly he recovered his breath; then raised himself to his feet to look toward the entrance. It would be open now, the way cleared. But, instead of sunlight, he saw utter dark. Where the mouth of the cave had been was blackness--and nothing else! He fumbled for his flash, and stood in despairing silence before what the light disclosed. The rock was black and shining about the mouth of the cavern. It had split like glass. In shattered fragments it filled the forward part of the cave. The whole roof must have fallen, and a crashing slide above had covered all. Chet was beside him; Harkness dared not look toward the girl coming expectantly forward. "We'll use more of the same," Chet suggested: "we will blast our way out." "And bring down more rock with each charge," Harkness told him tonelessly. "This means we are--" Diane had overheard. Harkness' pause had come too late.