International Crime Detective

Against the wishes of her stepfather, Mary Sutherland has become engaged to Hosmer Angel. On the morning of their wedding Hosmer elicits a promise that Mary will remain faithful to him "even if something quite unforeseen" occurs, then mysteriously disappears en route to the church. Holmes deduces that Hosmer was Mary's stepfather in disguise, the charade a bid to keep Mary a spinster and thus maintain access to her inheritance.

Prime Minister, Herbert Asquith, and Inspector Gregson, long out of touch with Sherlock Holmes, meet the great detective on 28 June 1914, the day of the assassination of Archduke Ferdinand in Sarajevo. The Germans have introduced a new code and it has baffled the British secret service. As international tensions increase and more messages in the new code are intercepted, the urgency to decrypt mounts, but Holmes is preoccupied with the events that form the narrative of His Last Bow.