Hercule Poirot met his lifelong friend, Captain Arthur Hastings, and solved the first of his cases to be published, "The Mysterious Affair at Styles". It is clear that Hastings and Poirot are already friends when they meet in Chapter 2 of the novel, as Hastings tells Cynthia that he has not seen him for "some years". Particulars such as the date of 1916 for the case and that Hastings had met Poirot in Belgium, are given in "Curtain: Poirot's Last Case", Chapter 1. After that case, Poirot apparently came to the attention of the British secret service and undertook cases for the
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,