Suddenly, I felt that awful agony through every nerve again, and I knew we had stumbled into more of Marnick's detector beams. This time we may have blundered far enough to set off an alarm, but I didn't especially care. I fell to the ground as the warning along my nerves persisted. For a minute I was almost violently ill. Luckily, the others stopped instantly. McGowan dragged me back and waited until I had recovered. "Our human beam detector. Lucky we've got you with us, Reed!" But there was no humor in his voice, in fact I caught a note of pity. I think he already realized, just as I was slowly beginning to-- But I shall not think of that. McGowan spoke a few words to Elson that we could not hear. Elson nodded obediently. We moved away at a sharp angle to the right, but now I noticed Elson did not accompany us. I was still dizzy and weak, but I clenched my teeth and determined to see this thing through to the finish. I guided us away from those beams. As near as I could determine, they rayed out in a sort of semi-circular barrier, invisible, of course. Carefully we skirted the edge of it, toward the far wall of the canyon that sheltered Marnick's house. How I stayed on my feet I cannot understand, for every step was an agony as the faintest out-reaches of those rays stabbed fiercely through me. The others, of course, felt nothing. "We've got to get past it," McGowan whispered tensely to me, "or we're finished!" I nodded curtly. I didn't know what McGowan had in mind, but I realized we had to get closer to Marnick's house. We came nearer and nearer to the canyon and then the power of the beams began to diminish. We pressed flat against the rocky walls and moved swiftly forward. Suddenly we were beyond the barrier. The squat stone dwelling was a bare fifty yards from us now, and we could see a little square of light from the side window. * * * * * We paused there in a huddled little group, wondering what McGowan's next move would be. Apparently he was waiting for something. And a second later we knew what it was, as a ringing alarm shattered the silence! I knew it must have been Elson out there who had set it off, according to McGowan's instructions. I glanced sharply at McGowan and he seemed satisfied, as he cautioned us to silence. Another square of light appeared and we glimpsed the tall form of Marnick in the open doorway. But he knew better than to remain there long against the light. He stepped quickly outside, but not before we glimpsed an atom-pistol in his hand. "This is it!" McGowan whispered. "I only wanted to get him outside." We moved silently across the space toward the side of the house that hid us from Marnick. There we could peer into the lighted window. I saw a large room quite like a library, and I was amazed at how richly it was furnished, with books and tables and tapestries and a fireplace at one end. It seemed utterly incongruous here on this dark, mad planet.