The Creatures, we soon realize, are Earth folk like ourselves, whereas Persons belong to a superior, cerebral (and, to us, alien) race. Safe in their antiseptic outpost, Persons occupy themselves with math, music, and the Dimension Game, while Creature Guards run the Colony and protect it from the filthy, hungry Creatures who overpopulate the city outside its walls. Within the colony is a young girl, Harmony, who has picked up from her atypical Person tutor and her own independent nature some very unorthodox fellow feeling for the Creatures. And just as Harmony is about to be sent back to the home planet for breeding, she develops some most un-Personlike feelings for fellow student Vector, who tells this. At 17, Vector is about due to have the Operation (Persons on Earth do not breed); but he finds that he would rather have Harmony. And so the two sneak out to live among the Creatures, where disease and hunger are still common, hoodlum gangs take over the streets at night, and everyone lives in fear of the Guards, who have come to consider themselves a separate race above the common Creatures. Unlike Harmony, Vector takes a while to accept the Creatures as equals despite the kindness some show when he is ill. The black-and-white inevitability of this issue makes the story's moral dimension static and unstimulating. However, Townsend succeeds admirably at creating a future world, filling it with solid figures, and characterizing the different classes and their different lives. And the plot, which involves the two young people in Creature miseries, a Guard takeover, and, at the very end, a popular revolution, is well grounded in this imagined world, well managed for absolute conviction, and well timed for high impact.