Hercule Poirot investigates a decades-old double murder case that remains shrouded in ambiguity and conflicting memories. The detective is approached by a novelist who seeks to uncover the truth behind the deaths of a husband and wife, an event long dismissed as a suicide pact or a crime of passion. Poirot must navigate the unreliable nature of human recollection, interviewing aging witnesses whose memories have faded or distorted over time. He faces the challenge of reconstructing a past that many would prefer to leave buried, utilizing his methodical approach to logic to pierce through the fog of long-held secrets.

This novel is often analyzed for its meta-fictional commentary on the act of writing and the nature of memory itself. Readers frequently note that the narrative serves as a late-career reflection on the themes that defined the author's extensive body of work. The pacing is recognized as more contemplative and character-focused than the high-octane mysteries of the author's earlier period. Critics often highlight the clever way the plot mirrors the aging process of both the detective and the creator. The work stands as a testament to the enduring appeal of the classic whodunit structure even when applied to the complexities of the distant past.