The arrival of a mysterious foundling into the Marlowe household triggers a series of inexplicable and lethal events that threaten to dismantle the family unit. Alan Marlowe, the father and narrator, attempts to reconcile his initial compassion for the abandoned child, Bonnie, with the mounting evidence of her malevolence. As his biological children suffer fatal accidents, Alan must navigate the isolation of his growing suspicions while his wife remains blind to the danger. The narrative framework, presented through Alan's first-person perspective, emphasizes his internal struggle between paternal duty and the chilling realization that he has invited a predator into his home.

This novel is frequently cited as a quintessential example of 1970s domestic horror, often compared to other works featuring malevolent children. Readers and critics alike note the effectiveness of the slow-burn pacing, which relies on psychological dread rather than overt gore. The narrative's strength lies in its ability to transform a mundane family setting into a site of profound terror. The story remains a notable entry in the genre for its exploration of how suspicion can erode the foundations of a household.