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 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.