A woman finds her life irrevocably altered after a chance encounter on a train leads to a clandestine and consuming affair. Olivia Curtis, a young divorcée, navigates the social constraints of 1930s London while grappling with the emotional fallout of her relationship with Rollo Spencer. The narrative, presented through a blend of third-person perspective and internal monologue, captures the tension between societal expectations and the private, often painful, reality of romantic longing. As the affair progresses, Olivia must confront the limitations of her autonomy and the fragility of her social standing.

This novel is widely regarded as a definitive exploration of the complexities of romantic obsession and the social pressures facing women in the interwar period. Critics often highlight the technical sophistication of the prose, noting how the author captures the nuances of internal thought and external social performance. The work is frequently cited for its unflinching look at the emotional toll of an affair that offers little hope for a conventional future. Readers often find the protagonist's vulnerability and the atmospheric rendering of London to be the most enduring elements of the narrative.