The idyllic domestic life of Harriet and David Lovatt is shattered by the arrival of their fifth child, whose presence threatens to dismantle their carefully constructed family unit. Harriet and David, committed to a traditional, large-family ideal, find themselves unprepared for the physical and psychological toll exerted by their son, Ben. As Ben’s behavior becomes increasingly aggressive and alien, the couple faces a widening rift between their expectations of parenthood and the reality of their son's nature. The narrative, presented in a detached, observational tone, tracks the gradual erosion of the Lovatts' social standing and internal stability as they struggle to reconcile their love for their children with the terror inspired by one of their own.

This work is widely recognized for its unsettling examination of the limits of maternal love and the societal pressures placed upon the nuclear family. Critics often highlight the author's ability to transform a domestic setting into a site of profound existential dread. The narrative is frequently discussed for its refusal to provide easy answers regarding the nature of evil or the responsibilities of parents toward children who do not conform to societal norms. Readers often find the book's clinical detachment to be its most disturbing feature, as it forces an objective look at a family's disintegration.