The narrator discusses how he is a member of a gentleman's club, a gentleman's club which has cards, billiards, a wine cellar, and a library. Tom was a fan of these books, but himself preferred a tall tale. There was a tradition, once a month, in the club on a certain day, for members of the club to tell an outlandish story for everyone. The oldest member of the club stands, who has never before spoken, and says that he expects to die in the next few days. So he intends to tell this tale before then, concerning a man he's sure many will consider fictional, Sherlock Holmes.
Holmes at this time was getting on in years and in declining health, having parted ways with Watson, who he had complained about only reporting the exciting cases, and not the ones where he sat back, asked a question or two, and had the solution. "Tom", he says to the old man who was at the time young, "Am I becoming senile?" When answered in the negative, he expresses dismay, for he calls a land in a fiction book nonfictional. He decides to investigate. Tom goes away for some time, but returns with a telegraph telling him to acquire a book from the British Museum called The Book of the Enemy by any means necessary. Tom heads to Baker Street and finds a note with instructions, but is dismayed to see that it calls him Watson, feeling for Holmes' sanity.
The instructions had Tom head to the Martian Embassy, wherein Holmes was chatting with the Martian Ambassador. The two felt that the book was the cause of both of their problems. When Tom inquired as to what problem the ambassador was referring to, he was shown through a telescope that the canals on Mars had disappeared. Holmes explains to Tom that they're living in a time of war, which Tom balks at, knowing nothing but peace recently between countries on Earth and Mars. But there are places other than those, and wars fought not with ships but, says Holmes, but with ideas reshaping reality.
When Tom woke up the next day, he read the morning paper to see a reality he didn't recognize. Russian Anarchist, Winston Churchill, and no Martians. He discussed with Holmes these occurrences, and found The War of the Worlds, which he thought was an account of history, while the author purported it to be a book of fiction. Holmes suggests that reality is changing because people are reading a specific book, The Book of the Enemy, which he intends to read. Tom instantly objected to this, as it would erase him from existence, but Holmes felt it was necessary, and that he could fight the perniciousness of the book more effectively as a fictional character. Tom kept an eye on his friend, even stories that were wholly fictional, and wondered if sometime he might do something worth becoming fictional over.
After the story was over, people asked Tom if any of it was true, including whether he would die or if they'd see him next week. Tom shrugged them off and said they'd hear from him sooner or later. The narrator went back to the club and found that the building had disappeared. Years later he found a book on a shelf, and it within it, it told the same story that Tom had told that night.
- Sherlock Holmes
- Martian ambassador
- Startled gentleman
- Stout man
- Holmes and Watson visited Ruritania several times to assist King Rudolf.
- Britain established an alliance with Mars after the Martians' attempted invasion of Earth.
- The author published a list of references in the story.
- The framing story was borrowed from P. G. Wodehouse's stories about the "Oldest Member".
- The narrator recalls Watson's stories about Holmes' "excursion across the moors" (The Hound of the Baskervilles) and his "wrestling match on a precipice" (The Final Problem). He also mentions Holmes' assistance to "Popes" (All-Consuming Fire) and an address in Belgravia (A Scandal in Belgravia).
- The hypothetical about a man named Reginald who served kippers was a reference to Wodehouse's character Jeeves.
- As noted in the story itself, Ruritania and King Rudolf originated from The Prisoner of Zenda.
- The men in the British Museum's Select Manuscript Room – the startled gentleman who spilled his papers, and the stout man who helped collect them – are Dunning and Karswell from M.R. James' Casting the Runes.
- The account of the Martian invasion of Earth is designed to be consistent with H. G. Wells's The War of the Worlds and Simon Bucher-Jones' Charles Dickens' Martian Notes.
- Holmes' comment about "continental orchestra" is a reference to George Bernard Shaw's complaints about the differences between how British and continental European orchestras tuned their instruments.
- The mentions of "squamous cephalopodic beasts" and "non-Euclidean geometry" are references to H. P. Lovecraft's work.
- Moriarty's The Dynamics of an Asteroid was first mentioned in The Valley of Fear.
- The "mock turtle soup and dodos' egg" are a reference to the novel Alice in Wonderland.
- History remembered the Martian Embassy as being burned down in the siege of Sidney Street. The siege was mentioned and compared to the Holmes novel The Red-Headed League in Ronald Knox's essay Studies in the Literature of Sherlock Holmes, which first applied the idea of "canon" to works of fiction.
- The phrase "every trace of romance" was intended to be a reference to Lawrence Miles' novel Dead Romance.
- The conception given of platonic objects in this story differs from how they're contemporarily framed.
- Tom dreams of demons trapped in pyramids. (TV: Pyramids of Mars, AUDIO: The Judgment of Sutekh)
- Sherlock Holmes aided a Pope in PROSE: All-Consuming Fire.
- James Moriarty wrote the book On the Dynamics of the Asteroid. (PROSE: The Death of Art)
- Moriarty's theory of relativity was later attributed to Albert Einstein. (TV: Four to Doomsday, The Last Sontaran, et al.)