I guess you see now why we on (_damn_ the name!) Project Hush were so concerned about security. But we felt pretty sure, before we took off, that we had plugged every possible leak. We had, all right. Nobody even knew we had raised ship. * * * * * We landed at the northern tip of Mare Nubium, just off Regiomontanus, and, after planting a flag with appropriate throat-catching ceremony, had swung into the realities of the tasks we had practiced on so many dry runs back on Earth. Major Monroe Gridley prepared the big rocket, with its tiny cubicle of living space, for the return journey to Earth which he alone would make. Lieutenant-colonel Thomas Hawthorne painstakingly examined our provisions and portable quarters for any damage that might have been incurred in landing. And I, Colonel Benjamin Rice, first commanding officer of Army Base No. 1 on the Moon, dragged crate after enormous crate out of the ship on my aching academic back, and piled them in the spot two hundred feet away where the plastic dome would be built. We all finished at just about the same time, as per schedule, and went into Phase Two. Monroe and I started work on building the dome. It was a simple pre-fab affair, but big enough to require an awful lot of assembling. Then, after it was built, we faced the real problem--getting all the complex internal machinery in place and in operating order. Meanwhile, Tom Hawthorne took his plump self off in the single-seater rocket which, up to then, had doubled as a lifeboat. The schedule called for him to make a rough three-hour scouting survey in an ever-widening spiral from our dome. This had been regarded as a probable waste of time, rocket fuel and manpower--but a necessary precaution. He was supposed to watch for such things as bug-eyed monsters out for a stroll on the Lunar landscape. Basically, however, Tom's survey was intended to supply extra geological and astronomical meat for the report which Monroe was to carry back to Army HQ on Earth. Tom was back in forty minutes. His round face, inside its transparent bubble helmet, was fish-belly white. And so were ours, once he told us what he'd seen. He had seen another dome. "The other side of Mare Nubium--in the Riphaen Mountains," he babbled excitedly. "It's a little bigger than ours, and it's a little flatter on top. And it's not translucent, either, with splotches of different colors here and there--it's a dull, dark, heavy gray. But that's all there is to see." "No markings on the dome?" I asked worriedly. "No signs of anyone--or anything--around it?" "Neither, Colonel." I noticed he was calling me by my rank for the first time since the trip started, which meant he was saying in effect, "Man, have you got a decision to make!" "Hey, Tom," Monroe put in. "Couldn't be just a regularly shaped bump in the ground, could it?"