- "Alone is what I have. Alone protects me."
- ―Sherlock Holmes
Jim Moriarty possesses the greatest criminal mind that the world has ever seen. Sherlock and John knew he would not stay hidden for long. Even they, however, never guessed the sheer scale and audacity of the crime that would propel Moriarty back into the headlines. The crime of the century. The Tower of London, the Bank of England and Pentonville Prison – all sprung open on the same day, as if by magic! But Moriarty's plans do not stop there...
Sherlock locks horns with his old enemy in one final problem that tests loyalty and courage to their very limits. Sherlock must fight for his reputation, his sanity and his life. But is he all he claims to be?
The episode opens with John Watson in his first meeting with his therapist for eighteen months. He struggles to explain the reason for the impromptu visit, but eventually chokes out the words, "My best friend, Sherlock Holmes, is dead". The episode then flashes back to three months earlier, with Sherlock receiving plaudits and gifts from various people for whom he has solved cases, along with much unwanted media attention.
Meanwhile, Moriarty has been freed from Mycroft's prison and proceeds to break into the Tower of London, where the Crown Jewels are kept, while simultaneously opening the vault at the Bank of England and unlocking all the cells at Pentonville Prison via his mobile phone. Before smashing the Crown Jewels' case, he writes the words "Get Sherlock" in reverse on the outside, to be seen by the security cameras. He then allows himself to be caught wearing the jewels and sitting on the throne.
Sherlock is called to testify at Moriarty's trial. Sherlock explains to the court that Moriarty is a criminal mastermind, a criminal for hire. During the trial Moriarty does not speak a word and does not even mount a defence. Even though he did not mount a defence against the charges and the Judge himself recommends Moriarty be found guilty, Moriarty is acquitted due to having threatened each of the families of the jury. After being acquitted, Moriarty visits Sherlock at his home and explains that he has plans for Sherlock. Meanwhile, John is summoned to see Mycroft, who explains that a number of professional assassins have moved into flats on 221B Baker Street, and asks him to watch out for Sherlock.
Sherlock and John investigate a kidnapping of the US Ambassador's children, which is a carefully orchestrated plot by Moriarty to implicate that Sherlock has been staging all of his cases himself. Lestrade arrests Sherlock, but Sherlock escapes with John. They also realize Moriarty's "Get Sherlock" has convinced the criminal underworld that Moriarty has given Sherlock the computer code he used to pull off his triple heist, and that it can bypass all security systems. A trail of bodies follow Sherlock as professional assassins fight over access to him.
They break into the house of a journalist poised to publish an expose on Sherlock. There, they discover that Moriarty has developed a fake identity, Richard Brook, who is supposedly an actor that Sherlock paid to pretend to be a master criminal. Now a wanted man with the papers ready to print the expose, based on Richard Brook's testimony, Sherlock launches a final gambit. Leaving John, Sherlock contacts Molly at the hospital, and, responding to an earlier conversation they had, admits he needs her help. John goes to Mycroft's office to question him, and learns that Mycroft divulged Sherlock's personal information during interrogations of Moriarty. Meanwhile, Sherlock deduces that the anti-security program was encoded in the tapping of Moriarty's finger during his earlier visit.
John finds Sherlock at the Barts lab, but leaves again after hearing Mrs. Hudson has been shot. Sherlock texts Moriarty, who meets him on the roof of the hospital, and claims that with the code he can erase Richard Brook electronically. Moriarty reveals that there is no code as the tapping is really a Bach tune and that Sherlock must commit suicide to complete his plan. Ready to do so, since otherwise Moriarty's assassins will kill John, Mrs Hudson and Lestrade, Sherlock realises that Moriarty has some sort of fail-safe and can call the killings off. Sherlock then convinces Moriarty that he would be willing to do anything to make him activate the fail-safe, so Moriarty kills himself after acknowledging commonality between him and Sherlock.
With no way to use the fail-safe, Sherlock calls John, who is rushing back from 221B Baker Street, after having found the report of Mrs Hudson's shooting false. Claiming that he was always a fake and explaining that this last phone call is his "note", Sherlock throws himself from the roof of St. Bartholomew's as John looks on from the street. After being knocked to the ground by a cyclist, John watches as Sherlock's crumpled and bloody body is carried away by hospital staff.
The episode returns to Watson's meeting with his therapist, but he is unable to open up. Later he visits Sherlock's grave with Mrs Hudson. While standing in front of his gravestone, he reaffirms his faith in Sherlock, and begs him not to be dead. From the shadows, Sherlock looks on silently as John walks away.
- "Because I owe you a fall, Sherlock. I. Owe. You."
- ―Jim Moriarty
- "I was so alone, and I owe you so much."
- ―Dr John Watson
I.O.U. is a recurring theme during this episode. It is spoken aloud by several characters, including Jim Moriarty, Sherlock Holmes, and John Watson and is also seen appearing in the background. It refers to Moriarty's promise to Sherlock that he will make him "fall".
The "I O U" motif appears in physical form three times during the episode. The first is in an apple that Moriarty carves and leaves at Baker Street, the second is spray-painted in three windows across from New Scotland Yard offices, and the third is graffitied on the street outside the 221 Baker St. street address. They are threats pertaining to certain individuals connected to those three locations, as Moriarty reveals on the roof of St. Bartholomew's Hospital at the end of "The Reichenbach Fall".
The last time the motif appears in the episode is at the end, during the graveside scene. John Watson says, "I was so alone, and I owe you so much."
- The episode's climactic scene is based on the short story "The Final Problem", in which Holmes and Moriarty square off. Watson's leaving Holmes to attend to Mrs Hudson mirrors his return to the inn in the original story, in order to attend a dying Englishwoman. Moriarty also mentions the short story by name while talking with Sherlock in 221B Baker Street about their final conflict.
- The filming of the visit of Moriarty to Baker Street pays tribute to William Gillette's 1899 play Sherlock Holmes and the 1945 film The Woman in Green. Moriarty's attempt to destroy Holmes's reputation and leading him to committing suicide by jumping from a building also has similarities to The Woman in Green.
- The kids' disappearance in the priory school is a reference to "The Adventure of the Priory School".
- Douglas Wilmer, who plays the cranky old man in the Diogenes Club, played Sherlock Holmes in a series of BBC television shows in the 1960s.
- When talking about the case of Henry Fishguard, Sherlock opens a old dusty book saying "Bow Street Runners: missed everything". The book actually is Memoirs of a Bow Street Runner, based on the private journal of Henry Goddard, one of London’s best paid detectives from 18th century.
- Moriarty listens to Rossini’s "The Thieving Magpie" while breaking in to the security systems.
- In the first sequence in which various newspaper headlines are shown, one story begins, "In a twist worthy of a Conan Doyle novella, Mr. Sherlock Holmes was yesterday revealed to be an expert witness at the trial of 'Jim' Moriarty."
- This newspaper was dated 5.10.11. Given the British dating system, this could be read as October 5.
- According to the newspaper in the promo for this episode, Moriarty left graffiti at the scenes of his crimes saying "Get Sherlock".
- According to the newspapers flashed on screen, Sherlock testifies at Moriarty's trial on 10 May, Moriarty walks free after the verdict and visits Baker street on 20 September. A second newspaper records him as 'vanishing' on Tuesday, 11.10.11.
- Sherlock and John investigate the ambassador's children case and later flee from police on 19 November, hence Sherlock's apparent suicide happens on 20 November. This is inconsistent with John's blog, which shows it happened in June. It is also in disagreement with the fact that John visits his therapist to help him deal with Sherlock's death, eighteen months after his last appointment.
- A newspaper with headline "United We Stand" is in the center of the shot between Moriarty and Sherlock in 221B.
- In the scene where Sherlock accuses Kitty Riley of believing Moriarty, a hanging on the wall saying "make believe" is in focus.
- The defence barrister is played by Ian Hallard, Mark Gatiss's husband.
- On Richard Brook's CV, one of the photos were credited to Arwel Jones. Arwel Wyn Jones is the production designer of Sherlock.
- After this episode, fans created the "I believe in Sherlock" campaign.
- Even more interesting was the numerous theroeis and YouTube videos on the internet that explained fans' ideas on how Sherlock could have survived. This was brought up in a behind the scenes moment with Steven Moffat and Mark Gatiss, who commented on one that was extremely elaborate.
- Nina Simone's song "Sinnerman" is featured in this episode.
- Towards the end of the episode, one of the Scotland Yard computers shows news of the death of Brian Lukis from "The Blind Banker".
- John's eulogy for his friend "You were the best man, the most human... human being that I've ever known" has a certain echo of Kirk's farewell to Spock during Star Trek II: The Wrath of Khan - "Of my friend, I can only say this: Of all the souls I have encountered in my travels, his was the most...human". It is another reference to Star Trek after "The Hounds of Baskerville".
- One of the teaser hints released for this episode was "01110100 01101000 01100101 01110010 01100101 00100000 01101001 01110011 00100000 01101110 01101111 00100000 01101011 01100101 01111001", which converts from binary into "there is no key".
- In the credits of Sherlock on Masterpiece Mystery on PBS, some of the letters were highlighted red. Letters from this episode spell out B-E-L-I-E-V-E.
- When Moriarty is getting ready to steal the Crown Jewels, the position of the gum he places on the glass to hold the diamond changes between takes. Sometimes it is by the bottom of the "E," sometimes it is to the right of the "T."
- When Sherlock and Jim are at the roof top and Sherlock laughs and comes back to Jim to tell him what he missed, it's clearly visible that his scarf is a little messed up, but when the shot is focused on him 2 seconds later, the scarf is perfectly straight.
- As Moriarty is writing "Get Sherlock" on the case of the Crown Jewels, one shot shows that he has already written the "She-" of Sherlock and the next shot shows him just starting to write it.
- In the scene when Sherlock is analyzing the bottom of the kidnapper's shoe, he finds traces of Glycerol/Glycerine/Propan-1,2,3-triol. The Glycerol molecule contains 3 hydroxyl groups each bonded to three carbon atoms. The show misrepresents the molecule as having 2 hydroxyl groups, and one unknown OE group, which is in fact not even a chemical compound.
- Watson's first view of Holmes after he has jumped is partially obscured by a truck. In the shot where he is shown being knocked over by a cyclist, the truck is no longer in shot, and the bus stop further down the street is clearly visible, however while he is falling, the camera position shifts and then goes back to the view along the street in which the truck is back, and partially blocking the bus stop.
- The code Moriarty tapped is 100010000000000001000000000001000000000000000001000100000000000100000000000000010000010000010000001, but the code Sherlock tapped is 100100000000000010000001000000001000000000100000000000001, which is shorter, and varied from the actual by the fourth digit.
- When Moriarty shoots himself, his gun is in his left hand. Right after the shot, as he falls to the ground, his hand is empty. When you see him next, lying down dead, the gun is back in his hand.
- When Sherlock is watching Moriarty's video in the cab, there is a glimpse of the driver in the rearview mirror who is clearly not Moriarty as he has white hair.
- Sherlock Holmes – Benedict Cumberbatch
- Dr John Watson – Martin Freeman
- Mrs Hudson – Una Stubbs
- DI Greg Lestrade – Rupert Graves
- Mycroft Holmes – Mark Gatiss
- Jim Moriarty – Andrew Scott
- Molly Hooper – Louise Brealey
- Kitty Riley – Katherine Parkinson
- Sgt Sally Donovan – Vinette Robinson
- Philip Anderson – Jonathan Aris
- Ella Thompson – Tanya Moodie
- Chief Superintendent – Tony Pitts
- Prosecuting Barrister – Jaye Griffiths
- Defence Barrister – Ian Hallard
- Judge – Malcolm Rennie
- Claudie Bruhl – Sydney Wade
- Max Bruhl – Edward Holtom
- Bank Director – Paul Leonard
- Prison Governor – Christopher Hunter
- Prison Warder – Tony Way
- Miss Mackenzie – Lorraine Hilton
- Reporter 1 – Samantha-Holly Bennett
- Reporter 2 – Peter Basham
- Reporter 3 – Rebecca Noble
- Gallery Director – Robert Benfield
- Clerk of the Court – Ifan Huw Dafydd
- Father – Michael Mueller
- Assassin – Pano Masti
- Diogenes Gent – Douglas Wilmer
- CID Officer - Chris Wilson
|Sherlock Holmes (Benedict Cumberbatch) • John Watson (Martin Freeman) • Mycroft Holmes (Mark Gatiss) • Jim Moriarty (Andrew Scott) • Greg Lestrade (Rupert Graves) • Molly Hooper (Louise Brealey) • Mrs Hudson (Una Stubbs)|
|Irene Adler • Mary Watson • Charles Augustus Magnussen • Eurus Holmes|
|"A Study in Pink" • "The Blind Banker" • "The Great Game"|
|"A Scandal in Belgravia" • "The Hounds of Baskerville" • "The Reichenbach Fall"|
|"The Empty Hearse" • "The Sign of Three" • "His Last Vow"|
|"The Six Thatchers" • "The Lying Detective" • "The Final Problem"|
|Unaired Pilot • "Many Happy Returns" • "The Abominable Bride"|
|"Sherlock: The Network" • Manga|