He looked for another second, then straightened and came toward us at a lope. "They line up," he said when he reached us. "The bottom of the hole in the cactus is right in the middle when you sight through the hole in the rock." "As if somebody came around and whacked the cactus regularly," Janus said, looking around warily. [Illustration] "To keep the line of sight through the holes clear?" I wondered. "Why not just remove the cactus?" "Religious," Janus explained. The gauntlet he had discarded lay ignored on the ground, in the shadow of the cactus. We went on past the ridge toward an outcropping of rock about a hundred yards farther on. We walked silently, each of us wondering if what we half-expected would really be there. It was. In one of the tall, weathered spires in the outcropping, some ten feet below its peak and four feet above the ground, was a round four-inch hole. Allenby sat down on a rock, nursing his ankle, and remarked that anybody who believed this crazy business was really happening must have holes in the rocks in his head. [Illustration] Burton put his eye to the hole and whistled. "Sixty feet long if it's an inch," he said. "The other end's just a pinpoint. But you can see it. The damn thing's perfectly straight." I looked back the way we had come. The cactus stood on the ridge, with its U-shaped bite, and beyond was the ship, and beside it the perforated rock. "If we surveyed," I said, "I bet the holes would all line up right to the last millimeter." "But," Randolph complained, "why would anybody go out and bore holes in things all along a line through the desert?" "Religious," Janus muttered. "It doesn't _have_ to make sense." * * * * * We stood there by the outcropping and looked out along the wide, red desert beyond. It stretched flatly for miles from this point, south toward Mars' equator--dead sandy wastes, crisscrossed by the "canals," which we had observed while landing to be great straggly patches of vegetation, probably strung along underground waterflows. _BLONG-G-G-G- ... st-st-st- ..._ We jumped half out of our skins. Ozone bit at our nostrils. Our hair stirred in the electrical uproar. "L-look," Janus chattered, lowering his smoking gun. About forty feet to our left, a small rabbity creature poked its head from behind a rock and stared at us in utter horror. Janus raised his gun again. "Don't bother," said Allenby tiredly. "I don't think it intends to attack." "But--" "I'm sure it isn't a Martian with religious convictions." Janus wet his lips and looked a little shamefaced. "I guess I'm kind of taut." "That's what I _taut_," said Allenby. The creature darted from behind its rock and, looking at us over its shoulder, employed six legs to make small but very fast tracks. We turned our attention again to the desert. Far out, black against Mars' azure horizon, was a line of low hills. "Shall we go look?" asked Burton, eyes gleaming at the mystery.