Alex Clark's honeymoon is interrupted by the re-emergence of Marcus Rogers and his evil band, The Seven Great Families. The group, with the help of a powerful alien nobleman - Ares of Helios - intend to depopulate the Earth and remake what remains in the image of Ares' home planet, Uor. But Ares' twin brother, Apollo, is determined to save both Earth and Uor from class-based dictatorships. Alex and Apollo are both caught in a race against the clock because Rogers has forced a group of noted scientists to develop an Uorian technology into a powerful weapon that will bring the leaders of Earth to their knees. Meanwhile, Apollo has been declared an outlaw on Uor and, reluctantly, becomes the leader of a movement to dismantle a dictatorship that has ruled the planet for thirty thousand years.