First published in The Sketch, on the 25 April 1923 (Issue 1578) and later collected in Poirot Investigates (1924). The story’s setting in the Poirot chronology is considerably earlier than most of the other stories in the Sketch series, apparently taking place shortly after the Styles case. Poirot has just taken up permanent residence in London and is not yet the famous, fashionable detective that he will soon become; Hastings, meanwhile, is still working for the army in an administrative capacity. In fact, the war is still very much ongoing and patriotism is the keynote of the tale – a keynote that is struck by Poirot himself. When visited by two government officials who hope to enlist Poirot’s help in finding the missing Prime Minister, the immigrant detective understandably enquires: ‘What made you come to me? I am unknown, obscure in this great London of yours.’ He has apparently…