Sir John Appleby, a distinguished Commissioner of the Metropolitan Police, navigates a series of complex criminal investigations that challenge his deductive faculties. Throughout these short stories, Appleby applies his methodical approach to solve puzzles that range from professional police matters to private inquiries. The narrative framework utilizes a series of self-contained cases, allowing the protagonist to operate within various social and professional environments. He faces adversaries who rely on misdirection and intellectual obfuscation, requiring him to maintain logical rigor to uncover the truth behind each incident.

Readers frequently highlight the author's ability to balance intricate plotting with a sophisticated, often playful prose style. Discussion often centers on the evolution of Sir John Appleby as a character, noting how his transition from active commissioner to retirement alters the tone of the investigations. Critics observe that the short story format allows for a concentrated display of the author's talent for misdirection and clever resolution. The collection is often cited for its adherence to the conventions of classic detective fiction while maintaining a distinct, intellectual edge that keeps the reader engaged throughout each mystery.