A young woman interrupts Hercule Poirot’s breakfast to confess to a murder, only to vanish before he can determine the truth of her claim. Poirot must navigate the complex social dynamics of 1960s London, moving between bohemian flats and established family estates to uncover the reality behind the girl's erratic behavior. He faces a web of deception involving hidden family secrets, potential mental instability, and a series of physical clues that suggest a far more dangerous situation than a simple confession. The narrative follows Poirot's methodical investigation as he attempts to distinguish between genuine guilt and the influence of external manipulation.

This novel is widely regarded as a significant entry in the later period of Christie's bibliography, reflecting the author's attempt to integrate the changing social landscape of the 1960s into her traditional mystery framework. Critics have noted the ingenuity of the plot, which relies on the reader's ability to discern truth from the unreliable testimony of the central characters. The work is frequently cited for its successful pairing of Poirot with Ariadne Oliver, a dynamic that provides both humor and narrative depth. While some readers find the shift in tone to be a departure from her earlier works, the consensus remains that the puzzle-solving mechanics are as sharp as ever.