Although last night’s Sherlock derived its title from Conan Doyle’s novel The Sign of Four, the two stories share only the most tenuous of connections.
However, here are my top ten instances of how The Sign of Three referenced both the original and other Holmes adventures.
‘Three’ versus ‘Four’
1. Mary, Mary, quite contrary
In the books’ timeline, Mary Morstan first appears in The Sign of Four. Watson is attracted to her and proposes, and the pair eventually wed. However, she dies (of unexplained causes) during Holmes’ absence between The Final Problem and The Empty House.
The TV stories have been produced in a different order which contradicts the original chronology. Mary and John meet between The Reichenbach Fall and The Empty Hearse, and marry in The Sign of Three.
2. Familiar characters
Major Sholto is already dead in the original story. He was Mary’s father’s friend rather than John’s commanding officer.
In the literary version, Jonathan Small is a one-legged man, implicated in the death of one of Sholto’s sons.
3. The Poison Giant
Sherlock mentions this case, which involves a dwarf with a blow-pipe. In The Sign of Four, Jonathan Small’s accomplice is a ‘small’ man who fires poison darts from a blow-pipe.
4. The Inexplicable Matchbox
Sherlock describes the mystery of a French decathlete found surrounded by 1,812 matchboxes, all empty except one. This relates to a previously published case, The Inexplicable Matchbox, on John’s blog, which he is unable to recount due to the Official Secrets Act. However, he does mention Sherlock dressing as a clown and Mrs Hudson being pushed out of a helicopter.
Can we make this into an episode? Please?
5. The Bloody Guardsman
This resembles The Adventure of the Crooked Man. Both are locked room mysteries where the victim is a soldier in an army camp (although the perpetrator and weapon differ).
6. G is for …?
For the second episode running, Sherlock gets Lestrade’s first name wrong: Gavin here, Graham in The Empty Hearse. It’s an understandable error: Conan Doyle only ever referred to ‘G. Lestrade’.
7. Absent friends
One of the telegrams Sherlock reads out is from Mike Stamford, Watson’s former student colleague at Barts. He introduced John to Sherlock in A Study in Pink and regularly comments on John’s blog.
8. Codewords (I)
Sherlock reuses his “Vatican cameos!” warning to John. He previously used it when opening Irene Adler’s booby-trapped safe in A Scandal in Belgravia.
Vatican Cameos is both an unwritten adventure mentioned in The Hound of the Baskervilles and a computer game from the 1980s.
9. Codewords (II)
Speaking to young Archie, Sherlock says, “Get this right and there’s a headless nun in it for you.” This is another coded ploy, referring back to the series’ unaired pilot.
10. Hiding in plain sight
A recurring theme in the TV series. Jeff, the serial killer in A Study in Pink, was a black cab driver (which itself echoes Jefferson the murderous cabbie in A Study in Scarlet). In The Empty Hearse, John does not recognise Sherlock behind the anonymity of a waiter’s tuxedo. And here Small is a faceless photographer, both when stalking the Bloody Guardsman and at the wedding.
One final note: all the cases mentioned by Sherlock in his speech have now been included on John Watson’s blog, including comments.
The third and final episode of Sherlock is on BBC1 next Sunday at 8:30pm.