When a nun is discovered dead within the walls of the Convent of St. Anselm, Inspector C.D. Sloan must navigate the cloistered silence of the order to uncover a killer. Tasked with investigating a crime that threatens the sanctity of the religious community, Sloan faces the challenge of extracting truth from witnesses bound by vows of silence and tradition. The narrative follows a classic procedural framework, emphasizing the methodical gathering of clues within a confined, atmospheric setting. As the investigation progresses, the detective must reconcile the rigid social structures of the convent with the messy, human motivations behind the murder.

This novel is widely regarded as a foundational work in the post-WWII English traditional mystery genre. Readers and critics often highlight the author's ability to blend a classic whodunit structure with a distinct, understated sense of humor. The introduction of Inspector C.D. Sloan is frequently cited as a high point, establishing a character who remains a staple of the series. The work is praised for its clever plotting and its effective use of a closed-circle setting to heighten the tension of the investigation.