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 partly because there is rarely a narrator to mislead. In "Murder on the Links," still largely dependent on clues himself, Poirot mocks a rival "bloodhound" detective who focuses on the traditional trail of clues established in detective fiction (e.g., Sherlock Holmes depending on footprints, fingerprints, and cigar ash). From this point on, Poirot establishes his psychological bona fides. Rather than painstakingly examining crime scenes, he enquires into the nature of the victim or the psychology of the murderer. He predicates his actions in the later novels on his underlying assumption that particular crimes are committed by particular types of people.