Hercule Poirot investigates the suspicious death of a wealthy spinster, whose only witness to the truth is a loyal fox terrier. When Emily Arundell dies shortly after a fall down the stairs, her family suspects an accident, but a letter sent to Poirot before her death suggests foul play. Poirot must navigate a web of greed and deception among the victim's relatives, all of whom stand to inherit her fortune. The narrative follows Poirot's methodical process as he untangles the motives of the suspects, relying on his keen observation and the peculiar behavior of the victim's dog, Bob.

This novel is widely regarded as a quintessential example of Christie's mastery in the Golden Age detective genre. Readers often highlight the unique inclusion of Bob the terrier, which adds a distinct layer of charm to the otherwise tense investigation. The narrative is praised for its intricate plotting and the clever way Poirot deciphers clues that others overlook. It remains a staple for fans of traditional whodunits who appreciate a well-constructed puzzle and a classic setting.