When Dr. Lancelot Priestley discovers that his friend Sir John Claverton has died under suspicious circumstances, he must navigate a web of family secrets to uncover the truth behind a suspected poisoning. Priestley, a man of sharp intellect and methodical habits, finds himself at odds with the initial medical assessment of his friend's sudden demise. He must contend with a household of potential suspects and a series of baffling, seemingly contradictory clues that obscure the killer's identity. The narrative follows a traditional investigative framework, emphasizing the logical deconstruction of evidence rather than high-octane action.

The work reflects the hallmarks of the Golden Age of detective fiction, prioritizing cerebral puzzle-solving over visceral thrills. Readers familiar with the genre will recognize the methodical, almost clinical approach that defines the Dr. Priestley series. The narrative relies heavily on the protagonist's ability to synthesize disparate facts into a coherent explanation for an otherwise inexplicable death. It serves as a representative example of the period's fascination with the intellectual triumph of the amateur detective over complex criminal schemes.