Penrun paid little attention to their preparations. His attention was centered on those two shining rods atop the Queen's silken palace. They now aimed at the ship in its new position. A strange idea flashed through his mind. Those rods had in some mysterious way put the elevating machinery of the _Osprey_ out of commission! Suppose the spiders turned them next on his own space-sphere up here on the peak? The thought sent a shudder through him. Visions of the final flight across the nightmarish, distorted granite, the running down and capture of himself and Irma, the paralyzing bite of the monsters in the cavern of the Living Dead flashed across his mind. Cold sweat stood out on his forehead. Instinctively his hand leaped to the propulsion control and hovered there. * * * * * Yet why hadn't the spiders attacked the ship, now that they had it helpless? It was not their usual tactics to give their victims a chance to free themselves. Why, why? There could be only one answer. They were waiting for something! Penrun's eyes glinted suddenly. "Irma," he said rapidly, "we are in serious danger. The spiders have obviously put the elevating machinery of the _Osprey_ out of commission. Helgers and his men are doomed to the Living Death as surely as though they were already lying in the silken hammocks. If the monsters choose, they could do the same thing to our sphere and doom us to the same fate. I believe they are waiting for something. While they wait we have a chance to get the treasure and escape. Shall we risk it, or shall we go while we know we are safe?" She looked up at him evenly. "If you think we have a fair chance to get the treasure and escape, I say let's risk it," she said firmly. "Good!" he exclaimed. "Here we go!" The little sphere slipped out of its cleft in the peak and dropped swiftly into the valley on the side opposite the Trap-Door City and its mysterious menace. Day was swiftly dying, and the lower passes of the mountains were already hazy with rapidly forming storm-clouds. "Look!" cried Irma excitedly. "What are those things?" Far in the distance a long line of wavering red lights snaked swiftly through the dusky valley toward them. Penrun picked up his binoculars. "Spiders," he announced. "Scores of them. Each is carrying a sort of red torch. I have a feeling that those are what the monsters of the Trap-Door City have been waiting for." He urged the sphere to swifter flight along the range. Miles from the Caves, he swept up over the peaks, and dropped down on the lowlands side. Dusk was deepening rapidly as he raced back toward the White River cataract under the pall of the gathering storm. * * * * * Among the boulders on the rough mountainside near the mouth of the Caves he eased the craft down to a gentle landing. "Wait here," he told Irma. "I'll investigate and see if it is safe to enter the Caves."