Outer Shell Engineer Buchanan has good reason for his belligerence. The task of maintaining the integrity of the habitat's hull involves walling off areas which have become contaminated by acids and toxins from the outside. His job is certain to herald an early, agonising death. The rules maintain a happy, productive and satisfying life, for the majority. The Keepers enforce the rules. The rules range from maintaining a peaceful environment to protection from illegal organisations that aim to destroy their secure environment and those who worship a deity. Keeper Dominic falls in love with a woman his parents discover to be religious. Her entire village is secretly taken to the cells. Knowing Buchanan will provide his best method of vengeance Dominic agrees to trust him in the inclusion of whatever plan the OSE has devised for his revenge. Expecting to die, Buchanan and Dominic have only one ambition: to get as far away from the habitat as possible.