Hercule Poirot sort of obsessive-compulsive" in Poirot. As mentioned in "Curtain" and "The Clocks", he is fond of classical music, particularly Mozart and Bach. In "The Mysterious Affair at Styles", Poirot operates as a fairly conventional, clue-based and logical detective; reflected in his vocabulary by two common phrases: his use of "the little grey cells" and "order and method". Hastings is irritated by the fact that Poirot sometimes conceals important details of his plans, as in "The Big Four". In this novel, Hastings is kept in the dark throughout the climax. This aspect of Poirot is less evident in the later novels,
Hercule Poirot behind as a "very unhappy old man". However, Poirot and Hastings reunite during the novels "The Big Four", "Peril at End House", "The ABC Murders", "Lord Edgware Dies" and "Dumb Witness" when Hastings arrives in England for business, with Poirot noting in "ABC Murders" that he enjoys having Hastings over because he feels that he always has his most interesting cases with Hastings. The two collaborate for the final time in "Curtain: Poirot's Last Case", when the seemingly-crippled Poirot asks Hastings to assist him in his final case. When the killer they are tracking nearly manipulates Hastings into committing murder,