1The Empty Hearse
Two years after his reported Reichenbach Fall demise, Sherlock Holmes (Benedict Cumberbatch) has been completely exonerated of the slander that was caused him at the hands of James Moriarty. The opening scene shows a version of how Sherlock might have faked his death: by jumping from the roof with a bungee cable, bouncing back and entering the building through a window, where Molly stood waiting for him. While Sherlock absconded, members of his homeless network put a mask on Moriarty's face so that he would look like Sherlock, and then dragged onto the street to the spot where Sherlock would have landed and sprayed him with fake blood. All while this happened, Watson was lying on the ground, his vision obscured, having just been run over by a cyclist, who was in on the plan and who hypnotised him to give the others extra time to plant the body, this however is shown to be a conspiracy theory of Anderson. Sherlock with the aid of Mycroft returns to London which is under threat of terrorist attack. John has moved on and has a girlfriend, Mary Morstan (Amanda Abbington), whom he intends to propose to in a restaurant, when Sherlock enters, disguises himself as a French waiter with a thick accent and visits John's table a couple of times before he notices who he is.Sherlock reveals that he death was fraudulent to John, who fuelled by anger, hits him more than a few times. Sherlock enlists Molly to assist him in the case of an underground skeleton behind a desk containing a manuscript: "How I did it" by Jack the Ripper, revealed to be a fake planted by Anderson (now a conspiracy theorist, driven by guilt over his role in Sherlock's defamation) to lure Holmes out of hiding. Later that day, Mary receives a text telling her covertly that John has kidnapped by unknown assailants and will die if he isn't rescued in time, along with a location. Sherlock and Mary come to his rescue on a motorcycle, and manage to drag him out of a pyre on which a Guy was about to be burned.
John and Holmes then return to solving Mycroft's terrorist problem, which is revealed to be planned by an "underground movement" in the most literal sense (i.e. a movement based in the London Underground). They discover that a key figure in the plot is a politician named Moran, who with his organisation plots to blow up the Houses of Parliament during an all night sitting on the Fifth of November (Bonfire Night), to vote on a new terrorist law. Near a never used Underground station, they manage to find an Underground carriage that was earlier seen disappearing with Moran on it, and find that it is rigged with explosives. Sherlock manages to defuse the bomb by turning the off-switch, but not before making Watson believe the bomb can't be defused, causing him to panic and reveal to Sherlock how much he has missed him, to his later embarrassment.
In a flash forward before Sherlock reveals he has defused the bomb, he is seen visiting Anderson and revealing to him how he faked his death as part of a plan to round up Moriarty's network. An alternate version of the faked death is shown, leaving it ambiguous to which one is true, if any of them. Sherlock tells Anderson that he and Mycroft had anticipated thirteen possible scenarios that could happen on the roof. Each possibility had a code name and a plan of action attached to it. Sherlock however, did not anticipated that Moriarty would kill himself. Thus, Sherlock texts his brother one of the code names ("LAZARUS"). His homeless network shut down the entire street and were at the ready. John, who had no idea all this was happening could be seen in the cab driving towards the hospital. When John came, Sherlock made sure he stood at the right spot so that his view of the bottom half of the building was blocked. The homeless network and Mycroft's people set a large inflated cushion which allowed Sherlock to fall on safely and trick everyone. All the people rushed to pull the cushion away and Sherlock ran to hide. Then, Molly who was near a window threw a body double on the ground (the same person who Moriarty used to frame Sherlock for the abduction of Rufus Bruhl's children). John, who had rushed to the scene, only saw a glimpse of the body before he was intentionally knocked down by the cyclist which stalled him and allowed Sherlock to take the place of the body double and put a ball under his armpit to momentarily give the impression of having no pulse. The people that surrounded him then poured blood around and on him to further make the illusion, thus allowing Sherlock to fake his suicide.
In the ending scene, a silhouetted figure with blue eyes wearing glasses is observed watching footage of Sherlock and Mary.
2The Sign of Three
John Watson and Mary Morstan are having their wedding. Sherlock Holmes, being John Watson's best man, rises from his seat to give the best man's speech, but he hesitates and is unsure of what to say. Flashbacks show that he had failed in writing the speech. Sitting in the audience and watching him are Lestrade, Molly, Tom, and Mrs Hudson, as well as Major Sholto, who is John's former commander. John was delighted when Sholto walked in, since he didn't reply to his invitation, and it is explained that Sholto lives in seclusion. He is suffering from criticism by the media, and death threats, after having lost a unit of newly trained soldiers in Afghanistan.
Sherlock grasps for material and starts giving a rambling narrative about an attempted murder he and Watson had worked on, the Bloody Guardsman: not long ago, a Grenadier Guard was found unconscious in a shower room, suffering from a stab wound, but the weapon couldn't be found, and there wasn't a route for the attacker to escape. Earlier, the guardsman had emailed Sherlock after suspecting that someone was stalking him. Sherlock reluctantly admits that the case was never solved.
Sherlock's narrative drifts to another case, the Mayfly Man; a woman who worked as a private nurse, several days after going to a man's apartment for dinner, found that the apartment was vacated, and moreover, that the man was listed as having died weeks ago. Sherlock and Watson swept that apartment but couldn't find clues. One thing was strange; the woman knew John's middle name. Afterwards, Sherlock chatted online with other London women who had a similar experience, but couldn't find a connection between them. He concludes in his speech that the perpetrator must have been a man bored with marriage. The man must have used disguises and broken into the homes of people who recently died, as seen in obituaries.
While moving to the toast, Sherlock suddenly freezes in realisation. Knowing that John Watson is a man who never uses his middle name, it is obvious that the woman must have seen it somewhere besides normal print. Specifically, in John Watson's wedding invitation, one of whose recipients was Major Sholto. Sherlock concludes that all of the women were working for Sholto and bound to confidentiality, being his gardener, security guard, etc, and private nurse. The perpetrator is trying to get close to him to attack him, and the current wedding is his chance.
Sherlock slips a note to Sholto and the latter returns to his hotel room, and gets his pistol in order to defend himself. However, Sherlock deduces again that the stabbing of the the guardsman might be linked, and spots the common element as the military uniform. Since the the guardsman collapsed in the shower, he must have been stabbed with a razor thin stiletto type blade beforehand, but with the military waistbelt firmly holding the flesh together, the damage wouldn't take effect until the belt loosened. They send Sholto to hospital and arrest the wedding photographer, who is found to be someone who wants to kill Sholto because his brother was one of the new soldiers that perished.
Afterwards, with the sun having set, people move to a different hall for a dance. Sherlock quietly reveals to John and Mary the three signs he has observed confirming she is pregnant, then, unable to find a dance partner, he departs from the venue alone.
3His Last Vow
Lady Elizabeth Smallwood is one of many victims of master blackmailer and media tycoon Charles Augustus Magnussen and asks Holmes to retrieve some incriminating letters for her. Having cultivated Magnussen's secretary Janine, Holmes breaks into Magnussen's office but is confronted by a mysterious black-clad woman, who shoots him. THAT mysterious black clad woman is none other than MARY WATSON!!! He recovers in hospital and goes after her to discover her identity and reason for wanting the blackmailer dead before he and Watson visit Magnussen at his country house for a confrontation where Sherlock shoots Magnussen dead.!!Sherlock is convicted. Mycroft somehow manages to release Sherlock of his conviction and sends him on a Six months mission..As soon as Sherlock leaves BOOOOM..Every television in England is flooded with a video; Guess Who's Back..Yes..it is MORIARTY! How?? We don't know; but yes, MORIARTY is back!!