Red Dog was squat, ebony, taper-nosed, distinguishable from the lithic structures dotting this section of Crater Arzachel only by its symmetry. The grotesque rock ledges, needle-sharp pinnacles and twisted formations of the plain clearly were the handiwork of a nature in the throes of birth, when volcanoes burst and the floor of the crater was an uneasy sea of white-hot magmatic rock. Red Dog was just as clearly the creation of some other-world artificer, a creature born of the intelligence and patience of man, structured to cross the planetary voids. Yet it seemed a part of the plain, as ancient as the brooding dolomites and diorites which made the floor of Arzachel a lithic wonderland. The tail of Red Dog was buried in the ash of the plain. Its body reached upward, canted slightly from the vertical, as if it were ready to spring again to the stars. The rocket launcher had been removed. Now it stood on the plain off to one side of the rocket, small and portable, like some deadly insect. The launcher bothered Crag. He wanted to destroy it--or the single missile that remained--but was deterred by its possible use if the enemy should land another manned ship. In the end he left it where it was. One of the numerous rills which crisscrossed the floor of the crater cut near the base of the rocket at a distance of about ten yards. It was a shallow rill, about twelve feet wide and ten feet deep, with a bottom of soft ash. Adam Crag studied the rocket and rill in turn, a plan gradually forming in his mind. The rocket could be toppled, its engines removed and an airlock installed in the tail section, as had been done with the Aztec. It could be lowered into the rill and its body, all except the airlock, covered with ash. Materials salvaged from the drones could be used to construct extensions running along the floor of the rill and these, in turn, covered with ash. This, then, would be the first moonlock, a place where man could live, safe from the constant danger of destruction by chance meteorites. He looked thoughtfully at the sun. It was an unbearable circle of white light hanging in the purple-black sky just above the horizon. Giant black shadows crept out from the towering walls of the crater. Within another twenty-four hours they would engulf the rocket. During the lunar night--two weeks long--the crater floor would be gripped in the cold of absolute space; the rocket would lie in a stygian night broken only by the brilliance of the stars and the reflected light of an earth which would seem to fill the sky. But they couldn't wait for the advent of a new day. They would have to get started immediately.