Gareth, from impoverished Wales, and Karen, from rich California, enter a high-school essay contest and win a free trip to the American moonbase. There they encounter Bethkahn, a stranded noncorporeal alien whose colleagues, millenia ago, were the enabling intelligence that sparked the evolution of ape into man. Gareth helps repair Bethkahn's ship, then leaves his body and joins her in the trip back to her home. An entertaining and appealing story, with real characters--silly, brash, but generous Karen who rubs proud, poor and desperate Gareth the wrong way, Even junior technician Bethkahn and her anxious ship seem plausible. Less convincing are some of the details--people behave as if gravity were earth normal; there are only vague explanations of how disembodied Karen is able to carry a piece of her ship to the moonbase, and coincidences abound. More fantasy than sf, but a good yarn anyway.