The twenty-year-old message carried a tone of foreboding. It was as though Dr. Merrill felt that the four remaining less-experienced men of his original crew of nineteen could not successfully bring the ship back to port. “So close to my dream of a satellite hospital and yet so far,” were his unhappy words. “And yet we shall try with all our might, my dear, to come home. This treasure of ours _must_ not go to waste. There is so much good that it can do.” The letter ended abruptly as Dr. Merrill wrote, “Fox has just called me forward. I think they may be having trouble. I’ll tell you all about it when I get back.” But of course neither Dr. Merrill nor anyone else ever told what had happened. Rock tenderly folded the brittle paper and tucked it away safely. His mother would cherish this last word from her husband. Rock knew now why his mother had scrimped and saved, working at the algae canning plant, to make him eligible for cadet school. But he didn’t know how hurt she must have been when he washed out. She hadn’t told him that. The days dragged by slowly. With only a backdrop of star smudges to look at and unpalatable meals of hard, ancient food to eat, it was not exactly an enjoyable trip. Added to this of course were the youths’ additional worries about the welfare of their two buddies and whether the _Northern Cross_ would hold together until the beloved sphere of Earth swam into view. When the ship moved into the environs of Luna, the weary five knew that Earth could not be far off. Ninety-nine per cent of their journey was already over. Rock studied the enlarging globe of Earth’s satellite. Its wrinkled, gray face shone dazzlingly bright under the full glare of the sun. The filtering glass was lowered over the forward port to cut down the brilliance. It was on the space day following that there occurred an incident that filled the boys with exuberant hope. They were almost at their closest approach to Luna. The gray desolate lands were right “below.” A crackling was heard over the automatically set radio. “Somebody must have picked up our signal and is trying to make contact!” Shep cried out. Rock moved to the console to begin cutting speed. Then all gathered around the radio. Hugh was the radio expert. He scooped up the mike and slid into the chair in front of the bank of knobs. “_SS Northern Cross_,” he said eagerly. “_SS Northern Cross._ Come in, whoever you are! Please come in!” The crackling continued. Then there was a fragment of voice that was quickly lost in a babble of sound. Hugh kept talking into the mike. “It’s that faulty antenna!” Rock groaned. The crackling continued. Just as Hugh was about to give up, a voice came in weakly again. It was a voice the boys had to strain to hear, but they caught the vital message: “Hugh—Rock!” it said. “We picked up your SOS. We’ve had to make an emergency landing on Luna.” “Leo!” Shep said. “It’s Leo!”