When a prominent government minister dies under suspicious circumstances during a routine surgery, Inspector Roderick Alleyn must navigate the insular world of a private nursing home to uncover the truth. The protagonist, Inspector Alleyn, faces a complex web of professional rivalries, hidden motives, and clinical precision that obscures the identity of the killer. He must rely on his keen observational skills and methodical interrogation techniques to dismantle the alibis of the medical staff and visitors present during the operation. The narrative unfolds through a traditional third-person perspective, emphasizing the logical deduction required to solve a crime committed within a highly controlled environment.

This work is widely regarded as a quintessential example of the Golden Age detective novel, showcasing the author's ability to blend social commentary with intricate puzzle-solving. Readers and critics often highlight the sharp characterizations of the medical staff and the authentic, if dated, procedural details that ground the mystery. The narrative style is noted for its wit and the polished, intellectual approach of Inspector Alleyn, which remains a hallmark of the series. The book is frequently cited for its clever manipulation of the 'locked-room' style mystery, ensuring that the tension remains high until the final revelation.