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 hostel, while in "Third Girl" (1966) he is forced into contact with the smart set of Chelsea youths. In the growing drug and pop culture of the sixties, he proves himself once again, but has become heavily reliant on other investigators (especially the private investigator, Mr. Goby) who provide him with the clues that he can no longer gather for himself. Notably, during this time his physical characteristics also change dramatically, and by the time Arthur Hastings meets Poirot again in "Curtain", he looks very different from his previous appearances, having become thin with age and with obviously dyed hair.