"There's a natural explanation, of course," he said. "My theory is that the moon rock is of some composition sensitive to the action of moon rays; somewhat as the metal selenium is to sun rays. The little circles over the top are, without doubt, its operating agency. When the light strikes them they release the mechanism that opens the slab, just as you can open doors with sun or electric light by an ingenious arrangement of selenium-cells. Apparently it takes the strength of the full moon both to do this and to summon the Dweller in the Pool. We will first try a concentration of the rays of the waning moon upon these circles to see whether that will open the rock. If it does we will be able to investigate the Pool without interruption from--from--what emanates. "Look, here on the chart are their locations. I have made this in duplicate for you in the event--of something happening--to me. And if I lose--you'll come after us, Goodwin, with help--won't you?" And again I promised. A little later he complained of increasing sleepiness. "But it's just weariness," he said. "Not at all like that other drowsiness. It's an hour till moonrise still," he yawned at last. "Wake me up a good fifteen minutes before." He lay upon the berth. I sat thinking. I came to myself with a guilty start. I had completely lost myself in my deep preoccupation. What time was it? I looked at my watch and jumped to the port-hole. It was full moonlight; the orb had been up for fully half an hour. I strode over to Throckmartin and shook him by the shoulder. "Up, quick, man!" I cried. He rose sleepily. His shirt fell open at the neck and I looked, in amazement, at the white band around his chest. Even under the electric light it shone softly, as though little flecks of light were in it. Throckmartin seemed only half-awake. He looked down at his breast, saw the glowing cincture, and smiled. "Yes," he said drowsily, "it's coming--to take me back to Edith! Well, I'm glad." "Throckmartin!" I cried. "Wake up! Fight!" "Fight!" he said. "No use; come after us!" He went to the port and sleepily drew aside the curtain. The moon traced a broad path of light straight to the ship. Under its rays the band around his chest gleamed brighter and brighter; shot forth little rays; seemed to writhe. The lights went out in the cabin; evidently also throughout the ship, for I heard shoutings above. Throckmartin still stood at the open port. Over his shoulder I saw a gleaming pillar racing along the moon path toward us. Through the window cascaded a blinding radiance. It gathered Throckmartin to it, clothed him in a robe of living opalescence. Light pulsed through and from him. The cabin filled with murmurings-- A wave of weakness swept over me, buried me in blackness. When consciousness came back, the lights were again burning brightly. But of Throckmartin there was no trace! CHAPTER VI "The Shining Devil Took Them!"