Driven by the grief of a hit-and-run tragedy, a father transforms from a writer of detective fiction into a cold-blooded seeker of vengeance. Frank Cairnes meticulously tracks the driver responsible for his son's death, navigating the moral ambiguity of his self-appointed role as judge, jury, and executioner. The narrative, presented through the protagonist's diary entries, forces the reader to confront the psychological toll of obsession and the blurred lines between justice and murder. As the hunt intensifies, Cairnes finds his own carefully constructed plan threatened by unforeseen complications and the scrutiny of those around him.

This novel is widely regarded as a significant entry in the canon of mid-century British crime fiction, noted for its clever subversion of genre expectations. Readers and critics often highlight the effectiveness of the diary format in grounding the reader within the protagonist's deteriorating mental state. The work is frequently praised for its intellectual rigor and the way it challenges the reader's sympathy for a grieving father turned killer. It remains a staple for those interested in the evolution of the psychological thriller and the darker side of the classic detective story.