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,
Parker Pyne Investigates comprises twelve of her fourteen stories featuring detective James Parker Pyne; the two remaining stories, "Problem at Pollensa Bay" and "The Regatta Mystery" were later collected in "The Regatta Mystery" in 1939 in the US and in "Problem at Pollensa Bay" in the UK in 1991 although these were originally stories featuring Hercule Poirot when they were first published in the "Strand Magazine" in 1935 and 1936 respectively. The book also features the first appearance of the characters of Ariadne Oliver, and Miss Felicity Lemon, both of whom would go on to have working relationships with Hercule Poirot in later