When a routine dental appointment ends in the violent death of a prominent practitioner, Hercule Poirot must untangle a web of deceit that links a seemingly simple suicide to a larger, more calculated conspiracy. Poirot is tasked with investigating the death of Henry Morley, a dentist who dies shortly after treating a patient, leading the detective to examine the lives of those in the victim's orbit. As he navigates the social strata of London, Poirot faces the logical challenge of reconciling a series of seemingly unrelated events with a singular, cold-blooded motive. The narrative employs a classic third-person perspective, focusing on Poirot's methodical observation and his reliance on the 'little grey cells' to expose the truth hidden beneath polite society.

This novel is widely regarded as a quintessential example of Christie's ability to weave complex, multi-layered plots around a seemingly mundane inciting incident. Readers often highlight the clever integration of the nursery rhyme theme, which serves as both a structural device and a chilling commentary on the nature of the crimes. The characterization of Hercule Poirot remains a focal point for analysis, as his clinical approach to human behavior contrasts sharply with the emotional volatility of the suspects. The work is frequently cited for its tight pacing and the satisfying, albeit intricate, logical progression that leads to the final revelation. It stands as a testament to the author's mastery of the traditional whodunit format.