Watson’s response to Holmes’s apology is one of the more touching rewards of the entire series. “ ‘You know,’ I answered with some emotion, for I had never seen so much of Holmes’s heart before, ‘that it is my greatest joy and privilege to help you.’ ” Only one other passage, to come a few years later, equals this intensity of feeling between the two men.

Further, “The Adventure of the Devil’s Foot” revisits another personal theme mentioned earlier: Conan Doyle’s long platonic love for Jean Leckie. One of the murderers in this story, Leon Sterndale, has had a long platonic love for Brenda Treginnis. “For years I have loved her. For years she has loved me.... For years Brenda waited. For years I waited.” She is killed, however, by her brother, Mortimer, who was hoping just to drive her insane so that he could inherit the family estate. Sterndale then avenges her death by forcing Mortimer Treginnis to breathe the same deadly fumes that Mortimer had used to kill his sister. Sterndale’s grief at the death of his beloved is so profound that once again Holmes becomes justice itself, letting the broken man go in peace, with the full assent of Watson and every reader with an ounce of pity.

Not long after this story, Conan Doyle had another occasion to change his writing in reaction to outside commentary, this time from a highly learned source. In 1912 Ronald Knox, who later became well known as a monsignor in the Catholic Church, published a talk he had given the year before to a student union about the eleven points common to the Sherlock Holmes stories. Conan Doyle read it, then sent Knox a polite, appreciative letter in response. But in his very next story, “The Adventure of the Dying Detective,” he intentionally set out to break the patterns so astutely adduced by Knox. No one likes to think his or her mind is an open book to other people. In the previous stories, the plots had mysteries for the reader to try to solve, but the framework for those plots was predictable. In “The Dying Detective” Conan Doyle varied some of those predictable elements. First, the story doesn’t begin as usual in Baker Street, but in Watson’s rooms during his marriage. Then the first words spoken are from the heretofore silent Mrs. Hudson, Holmes’s landlady. Holmes doesn’t have a visitor bring him a case, nor does he go out to survey the scene of any mystery: The action comes to him. But then Conan Doyle plays a really crafty trick on us. After reading of his rheumatism and seeing the series of mistakes Holmes had made in the last few stories, we have been conditioned to the physical weaknesses age has visited on him. When he seems to be dying from a rare tropical disease, his infirmity is believable. Then Conan Doyle turns the tables on our expectations when Holmes, once again his invincible old self, pops up, calmly lights a cigarette, and informs a killer that the jig is up.

Conan Doyle continued until 1917 to publish the stories that ultimately formed His Last Bow. He took a break after publishing “The Dying Detective” in December 1913 to start a more substantial project. Out of the blue, and to the delight of his publisher, Conan Doyle wrote to the Strand in January 1914 that he had already written half of a new Sherlock Holmes novel. The last time he sent the Strand a Holmes novel, The Hound of the Baskervilles, sales of the magazine shot up by 30,000 copies. Conan Doyle finished his first and only draft by mid-April, but the novel didn’t appear in serialization in the Strand until September, after the Great War had begun. The last chapter concluded in May 1915. It was also serialized in the United States by the Associated Sunday Newspapers, which published a Sunday magazine as a supplement to the regular newspaper, much like Parade Magazine in the United States today. The U.S. version was printed once a week, while in England the Strand published chapters once a month, so the novel actually first appeared in full in the United States.

Conan Doyle expressed his apologies to his English editors for contributing only this trifling distraction instead of something more important to the war effort.