- This episode references other episodes far more than it does the original stories, as it wraps up many dangling ends.
- “The Final Problem” in the book features Sherlock’s facing off with his greatest nemsis, Moriarty, who invades his rooms and plays tricks on him and his friends. This is a reimagining, with a new, greater nemesis.
- A crashing plane with everyone asleep references “A Scandal in Belgravia.”
- Sherlock does pantomime to provoke confession – a technique he uses in several stories and the movies too. Of course, there’s fourth wall breaking as it’s not clear to the audience whether this is dream or hallucination.
- Just as the pair did with Mary in “His Last Vow,” Watson tries to make Moriarty a client. “This is not one of your idiot cases!” he insists. Obviously, it actually is.
- 221B Baker Street is burned in the short story “The Final Problem.” Still, the damage isn’t permanent.
- The Musgrave ancestral home with bad grave dates and a rhyme that goes unsolved for decades (one even called “her little ritual”) certainly references “The Musgrave Ritual.” This story deals with a rhyme passed down through generations concealing a hidden treasure and a treasure hunt to find it around the estate. On the show, it goes unsolved for decades. The line of “Sixteen by sixteen” appears in both and in both the hero digs under a tree.
- At last, the audience discovers what made this Sherlock cut off emotion. Several films have attempted to solve the puzzle.
- The creepy girl with a creepy song reflects several episodes of Doctor Who, especially “The Empty Child.”
- Facing death, the men banter about The Importance of Being Ernest…Mycroft played Lady Bracknell. In fact, this is a story about a long-lost brother and Lady Bracknell is keeping all the secrets.
- Sherlock Holmes is known for costumes. The episode plays this up with his sister as a master of disguise and Mycroft joining in with a fake-out for the audience. Eurus shares her brother’s skill at violin. He’s bribed with a Stradivarius in The Private Life of Sherlock Holmes.
- John gets in “Vatican cameos,” the danger signal used in several episodes.
- Eurus’s cruel game is very similar to the one Moriarty plays with Sherlock in “The Great Game” – cold cases with hostages and a ticking clock. She even plays tapes of Moriarty to enhance the connection. There’s some evidence it was his plan.
- The first puzzle asks Sherlock which of three Garrideb brothers pulled a trigger. This references the story of the Three Garridebs, though this doesn’t have three brothers, only two pretending to the name.
- The coffin lid puzzle references the coffin mystery seen in “The Disappearance of Lady Frances Carfax.” A more important plot point is furthering the Sherlock-Molly relationship. There’s also a quick Irene reference.
- Sherlock’s childhood best friend was Trevor – also his best friend in “The Adventure of the Gloria Scott.”
- Flash of Eurus notes that “Deep water” is always an issue for Sherlock as flashes appear of the swimming pool from “The Great Game” and the Reichenbach Falls from “The Abominable Bride.”
- Sherlock goes to rescue and support his sister when she’s exiled…much as he did with Irene.
- Mary’s final speech (marked with “Miss Me” on the disk) serves as a farewell to the character and also salutes and evaluates their partnership.
- When the pair put their apartment back together, they scatter their icons about – a chalkboard from “The Dancing Men,” famous bulletmarks and jackknifed correspondence. There’s also the smiley face from the show and a creepy doll and scarecrow from unspecified cases.
- The title would make this a fitting end to the series, but in fact, season five has been plotted and will likely be made when the actors have an opening.
If you enjoyed this, I recommend Sherlock: Every Canon Reference You May Have Missed in BBC’s Series 1-3 now in Kindle and Paperback.