They had seen the three men return to the ship, but others might have gone to the Caves after that. Penrun made his way down the slope to the lip of the cataract and the yawning blackness of the abysmal gorge below it. Overhead the storm was gathering swiftly, and the saffron light of the dying day illuminated the plateau eerily. Half a mile away the Trap-Door City shimmered fantastically in the uncertain light. Penrun repressed a shudder. The Devil's own playground! Thank God, he and Irma would be out of it soon! He crept down the narrow path that led under the ledge of the trickling cataract. Outside, a bolt of lightning stabbed down from the darkened heavens. Its lurid flash revealed the huge figure of a man, pistol in hand, beside the entrance to the Caves. Too late to retreat now, even had he wished to. Penrun's weapon flashed first. A scream of pain and fury answered the flash, and the man's pistol clattered down on the rock. The next instant Penrun was helpless in the clutch of a mighty pair of arms that tried to squeeze the life out of him. "Burn, me, will ye, ye dirty scum!" roared the giant of a man tightening his grip. "I'll break your damned back for ye and heave ye into the gorge!" Penrun writhed frenziedly, trying to twist his pistol around against his enemy's back, while they struggled desperately about the ledge above the dizzy blackness of the gorge. But the pistol struck the wall beside the entrance and fell under their trampling feet. Penrun was gasping in agony at the intolerable pain in his spine. Darting points of light danced before his eyes. Then from the opening in the rock showed a beam of white light and a man slowly emerged from the Caves. The grip on Penrun relaxed slightly as the man came toward the two combatants. Penrun could distinguish him closely now. A heavy, pasty face with liquid black eyes and a crown of thinning hair. Helgers! He was staggering and grunting under the weight of a heavy metal box. * * * * * "What's the matter, Borgain?" he asked. "Got this bird, Penrun, we been waitin' for!" "We don't need him, now that we already have the treasure. Still, it's a good thing we found him. Just as well to have no tales circulating about the Universe about our find. Toss him into the gorge, and go down and watch the other three chests until I get--" "Dick, Dick!" Irma's excited voice floated down from up among the boulders. "The spiders with those red cylinder torches have arrived! They are attacking the _Osprey_!" Helgers jerked up his head. "Why, if it isn't the little spitfire!" he exclaimed in pleased astonishment. "I thought the damned spiders had eaten her long before this. Rather changes things, Borgain. I'll just go on up and let my little playmate know I am here. Toss our friend over the edge there, and bring up another treasure chest." "What was that she was sayin' about the spiders attackin' the _Osprey_?" Borgain's voice was anxious.