Because of his small size, seventeen year old Christopher, a British boy, was chosen to man a high altitude rocket to photograph the strange dome-shaped protuberances which appeared suddenly on the moon's surface. At Woomerama, an Australian desert test site, he was trained for his mission. But before blast-off it became apparent there had been a security leak. Chris realized the identity of the spy only after the rocket was fired. Quick thinking and luck brought him back to earth with the vital information. Neither the Russians nor any other nation on earth had established the structures -- but some entirely unknown force from space. Moving facilely, with unflagging action and suspense, this seems more an atteation of contemporary developments than many of the season's fictional forays out-of-this-world. Minimal hocus-pocus, maximal story-telling.