cautiously toward the spot where he had fallen. He was gone. The rain had washed away any traces of blood that might have remained.

While Penrun hesitated, the roar of the tempest was split by a man's scream of agony. A lurid flash of lightning an instant later revealed a gigantic spider down by the cataract with Helgers' struggling body in his mandible jaws. Returning blackness blotted out the scene.

Irma's pistol stabbed a ray through the driving rain at the hideous monster. Instantly its grating roar for help rang out, and a group of red lights from the doomed Osprey across the plateau, detached themselves from the others and came streaking for the cataract.

Penrun seized the heavy treasure chest and staggered to the sphere.

"Hurry, here they come!" screamed the girl.

He fell through the door with his burden just as the foremost monster leaped the river. The next instant Irma sent the sphere rocketing upward. Just before they plunged into the clouds they caught a last glimpse of the Osprey with her ray guns melted off by the red cylinder torches, and great holes gaping in her sides through which the monsters were carrying out the members of the crew to their cavern of the Living Dead.

As the sphere burst through the storm cloud into the frigid air above it, Irma gave a cry and pointed at the peak where they had hidden in the sphere. The peak was now alive with moving red lights of monsters searching vainly for them. The scene dropped swiftly below as the sphere gathered speed for its homeward journey.

"We got only a small portion of the treasure, but it will be enough," said Penrun. "After we pay your family's debt, I want to spend a hundred thousand or so for a specially chartered battle-sphere which will come back here to Titan. If the Interplanetary Council will do nothing about the Trap-Door City, I shall, independently. Not rays, but good old primitive bombs such as they used back in the Twentieth Century. I'll blow the hellish place off the face of the map and with it the cavern of the Living Dead. I think those lying in the hammocks would thank me for releasing them in that way."