At the pool, Moriarty tells his men to kill Sherlock and John. Sherlock aims his gun at the explosives pack that was wired to James, and suddenly Moriarty’s phone rings. He asks if he can answer it and Sherlock tells him to go ahead. Disgusted, Moriarty takes the call, and then screams at the caller, telling him to repeat it. He warns that if the caller is lying, he’ll hunt the person down and skin them alive. Satisfied, Moriarty then apologizes to Sherlock, telling him that it’s the wrong day to die. Sherlock asks if he got a better offer, and Moriarty says that Sherlock will be hearing from him. He walks away, telling the caller that if he has what is claimed, he’ll make him rich. The snipers leave as well and John wonders what happened. Sherlock figures that someone changed Moriarty’s mind and wonders who.
In an apartment, a woman named Mrs. Adler approaches “Her Highness” and prepares to discipline her.
Back at 221B Baker Street, John is typing a blog on their recent exploits. Meanwhile, Sherlock tries to find a case that isn’t boring. Lestrade calls him in to examine a dead woman covered in speckles, but Sherlock isn’t impressed. John continues to blog about their cases, while Lestrade calls them in on a case about a suspected terrorist responsible for a jetliner crash in Germany. The suspected terrorist is dead, stashed in a car trunk nearby. Sherlock is unable to come up with a suitable theory, but is disappointed when John blogs about his failure. When he complains, John points out that the web site has received more hits than from any of Sherlock’s successes.
Lestrade then calls Sherlock and John to a theater to investigate a crime. The press gathers outside to get photos of Sherlock now that he has a public reputation. Sherlock is less than thrilled that he’s become a phenomenon as a “net detective.” Meanwhile, Mrs. Adler sees a photograph of Sherlock and then calls someone and says that it’s time.
Back at Baker Street, Mrs. Hudson is cleaning up as best she can when a man comes in, mutters “the doors,” and collapses. She calls for Sherlock and John, who interview the man when he wakes up. The man, Phil, explains that fourteen hours earlier, his car stalled while he was driving in the countryside. He saw a hiker in a red jacket standing across a field but went back to trying to start his car. When it backfired and Phil looked up, the hiker had collapsed. Phil went to investigate and discovered that the hiker in the red jacket was dead.
The DI in charge, Carter, takes a call from Lestrade, who suggests that he let Sherlock examine the crime scene. However, it’s John who drives to the crime scene and transmit images via wi-fi. Sherlock is at home, ignoring the doorbell. John tells him that the hiker was killed by a single blow to the back of the head from a blunt instrument, which is nowhere to be found. Carter suspects Phil, but Sherlock points out that there’s no reason he would call the police in if he was the murderer. Sherlock directs Carter to the nearby stream, but then Mrs. Hudson lets in the two men at the door, who turn off Sherlock’s computer and say that he’s coming with them.
John has no idea what is going on, and a helicopter arrives to transport him.
Sherlock examines the man who came in, Plummer, and tells him that he knows exactly where they’re going.
John is taken to Buckingham Palace where he finds Sherlock, still wrapped up in a bed sheet. After a moment’s silence, they both burst into laughter at the absurdity. As they wonder why they are there, Mycroft comes in and tells them to behave. He points out that the mystery of the dead hiker has an obvious solution and Sherlock agrees, and Mycroft tells them they have a new case. The Queen’s representative comes in and admits that his client is a big fan of John’s blog. Sherlock refuses to deal with an anonymous client, but as he walks away Mycroft steps on his sheet, rendering him naked. Unimpressed, Sherlock threatens to keep going and Mycroft finally tells him that it is the highest in the land.
Sherlock finally puts on his clothes and Mycroft explains that there is a criminal matter and they need Sherlock to keep the investigation confidential. He shows Sherlock a photo of a woman, a woman that Sherlock doesn’t recognize, and explains that she’s been at the center of two scandals in the last year, and ruined the marriage of a novelist by having an affair with both participants simultaneously. Mycroft says that the woman is named Irene Adler, who works professionally as a dominatrix known as “The Woman.”
At her apartment, Irene receives photos of Sherlock being taken going into Buckingham Palace.
The representative admits that Irene has photos of someone of significance to his employer. Mycroft reluctantly admits that the someone of significance is a young female, and that there are a considerable number of photographs. When Sherlock wonders what the case is and tells them to pay Irene, Mycroft tells him that Irene contacted them and said that she had the photos, but she has no intention of using them for blackmail. Intrigued, Sherlock agrees to take the case and leaves, telling Mycroft to text him the detail. He assures them that he’ll have the photographs by the end of the day, asks the representative for a box of matches since he knows that his employer smokes, and leaves. As they go, Sherlock explains that he knew that their employer smoked because there was an ashtray in the room.
Irene receives more photos of Sherlock and John. She then calls in her assistant Kate and says that they’re going to have a visitor and she’ll need a long time to get ready.
Once Sherlock has Irene’s address, he goes through his closet for the proper costume. He and John then drive to two blocks short of the address and get out. Sherlock, dressed as a priest, tells John to punch him in the face. When John hesitates, Sherlock punches him to provoke him into fighting back. John hits him repeatedly.
Kate helps Irene with her makeup and then goes to the door when someone rings. It’s Sherlock, who claims that he’s been attacked and robbed. Kate lets him in and John follows, saying that he’s a witness and a doctor. She leads Sherlock to the parlor and Irene comes in to see him, naked. She removes Sherlock’s priest’s collar and calls him by name. John comes in and is suitably surprised, and Irene invites him to sit down. She admits that she knows they were in the palace, while Sherlock is stumped since she has no clothing or traces to give him any clues. Irene has figured that John punched him, and John asks her to put something on.
Sherlock offers Irene his coat and she then asks about the case of the dead hiker. John is surprised she knows about it, and Irene says that she knows a policeman and what he likes. She assures Sherlock that he isn’t going to get the photographs, and he tells her that the hiker wasn’t murdered and the photos are in the room. When he realizes that his deduction is correct, Sherlock tells John to man the door into the parlor. Once John goes outside and closes the door, Sherlock tells Irene to think back to what happened in the field. She says that there’ll be a backfire, and Sherlock says that noises are important.
Right on cue, the smoke alarm goes off as John sets a magazine on fire. Irene glances instinctively at the mirror and Sherlock follows her gaze. He finds the secret catch, revealing a safe, and tells John to turn off the smoke alarm. Before he can, three men come in and shoot out the alarm.
Sherlock examines the keypad on the safe and tries to deduce the six-digit combination. Irene tells him that she’s already told him the combination and tells him to think. The three men come in with John and order everyone down on the floor. Their leader Neilson demands the safe contents and Sherlock realizes that he’s American. Neilson figures that Sherlock has the combination, and doesn’t believe his denials. The man also notes that Irene knows the second combination that will summon the police. When Sherlock still professes ignorance, Neilson tells his man Archer to shoot John. Sherlock finally offers to open it, turns, and enters the correct combination. Realizing that it’s booby-trapped, Sherlock opens it and ducks. The gun inside fires and shoots Archer. Sherlock takes out Neilson and Irene disarms the third man and then clubs him unconscious. Sherlock grabs the cell phone with the photos from the safe, goes outside, and fires two shots into the air to summon the police.
Sherlock goes back inside and Irene demands the photos back. Sherlock confirms that the camera is security-locked and doesn’t believe that she kept copies. Irene insists that the photos are her life and that she’ll die rather than let him take it. Unimpressed, Sherlock goes to find John. John has found Kate, who was knocked out by the intruders. Irene suggests that John check the back door, and then stabs Sherlock with a drugged needle. When he refuses to give her the camera phone, she whips him with a riding crop until he drops it. Irene tells the stunned Sherlock to tell his client that the photos are safe with her and she’ll only use them as insurance. She tells Sherlock to remember her as the woman who beat him and heads for the window. John comes in and Irene tells him that the drug will wear off in a few hours. As she goes, Irene tells John that Sherlock was paying attention to her after all: the safe combination was her measurements.
Sherlock imagines Irene coming to 221B Baker Street while he’s asleep, returning his coat, and telling him how the hiker was killed: by a boomerang thrown by an experienced sportsman, recently returned to England, which was washed downstream. Later, he wakes up and asks John where Irene went. John assures his friend that Irene wasn’t there and tells him to stay in bed. As John leaves, Sherlock hears a woman’s ecstatic sigh as a tone from his cell phone, in his coat pocket hanging on the door. When he checks it, he finds a message from Irene, “Till next time, Mr. Holmes.”
The next morning, Mycroft comes to the flat to see Sherlock and John. Sherlock assures his brother that the photographs are safe in Irene’s hands. Mycroft is skeptical but Sherlock advises him to leave Irene alone. Irene’s tone rings on Sherlock’s cell phone and he hastily takes it, while complaining that Mycroft knew that the assassins, CIA-trained, were going to be there at the same time. Sherlock gets another message with the same tone, asking how he’s doing. While Mycroft takes a call, John asks Sherlock about the tone and his friend admits that someone got ahold of his cell phone and personalized their caller ID. Mycroft comes back and Sherlock asks what else Irene has that the Americans are so interested in. He realizes that something big is coming and Mycroft tells him that Irene is no longer his concern.
Come Christmas Eve, John and Sherlock celebrate and have Lestrade, Mrs. Hudson, John’s current girlfriend Jeanette, and Molly. Lestrade explains that he and his wife are back together and will be going to Dorset in the morning, but Sherlock can’t help telling him his wife is sleeping with a PA teacher. As he talks, Sherlock notices that the counter on John’s web counter is still at 1,895. John will be going to see his sister, who is sober, and refuses to listen to Sherlock deduce otherwise. Sherlock has also deduced from one of Molly’s presents that she has a new boyfriend and is going to be seeing him that night. However, he discovers the present is for him. Molly starts crying and Sherlock apologizes, kisses her on the cheek, and wishes her a Merry Christmas.
The tender moment is interrupted when Irene sends another text message with her distinctive tone. John points out that Irene has sent 57 text messages. The current one simply says, “Mantelpiece.” Sherlock checks and finds a new present in the same shade of lipstick as Irene’s. He excuses himself and goes to his bedroom, opens the present, and discovers that it’s Irene’s camera phone with the photos. Sherlock calls Mycroft and tells his brother that they’re going to find Irene dead that night.
Later, Mycroft calls Sherlock to the morgue at St. Bartholomew’s Hospital. Molly is there and warns that the corpse’s face is bashed up. Once he sees her naked body, Sherlock confirms that it’s Irene and leaves. Mycroft goes after him as Molly wonders how Sherlock recognized the corpse from her naked body. Out in the hallway, Mycroft offers him a cigarette and Sherlock accepts, and then asks his brother how he knew Irene was dead. Sherlock explains that when he received the camera phone, he knew that her life depended on it and she chose to give it up. Mycroft asks about the photos and Sherlock wonders why they don’t care, and his brother says there’s no advantage in it. Sherlock wishes his brother a Merry Christmas as he walks away. Mycroft then calls John to tell him that Sherlock is on his way, and asks if they found the cell phone. When John wonders if he needs to stay with Sherlock despite his plans, Mycroft insists and hangs up. John apologizes to Jeanette, who insists that he’s a great friend and then storms off.
Sherlock comes in and tells John that he hopes he didn’t mess up his sock index. He then plays his violin through the week, refusing to eat. When John and Mrs. Hudson come in, they find him composing. Sherlock suddenly points out that the blog counter is still at 1,895. He enters the number into the cell phone but it’s not the correct password, and it informs Sherlock that there are only three attempts remaining. He tells John that the counter is faulty and goes back to composing. As John goes, he asks Mrs. Hudson if Sherlock has any kind of relationship and the housekeeper admits that she doesn’t know, and they could never know what goes on in his head.
John goes out and finds a beautiful woman waiting for him. She asks if he has any New Year’s plans and John is glad to take her up on her offer. When he asks what she has in mind, a car pulls up and John assumes that she works for Mycroft. They go to an abandoned factory and the woman sends him on ahead, and then calls to tell her employer that John thinks that it’s Mycroft. Meanwhile, John continues on and finds himself face-to-face with... Irene. He tells Irene to tell Sherlock that she’s alive, but she figures that Sherlock would come after her. John asks how she faked her test and Irene explains that she tampered with the DNA records on file for her. She admits that she made a mistake and needs the cell phone back, and wants John’s help. John refuses and tells her again to tell Sherlock that she’s alive. She wonders what to say and explains that she’s been flirting at Sherlock via text message but he never replied. When John objects, Irene asks if he’s jealous, and then sends Sherlock a text message inviting him to have dinner with her.
As they talk, they hear the tone go off on Sherlock’s phone. As John goes after his friend, Irene tells him not to.
Sherlock returns to Baker Street and notices that the door has been forced. He goes in and realizes that several men hauled Mrs. Hudson up the stairs. Sherlock goes into his flat and finds Neilson holding a gun to the housekeeper’s head. Neilson asks for the camera phone and Sherlock realizes that he beat Mrs. Hudson for the information. He tells Neilson to order his men out and he reluctantly agrees. Once the two men leave, Sherlock invites Neilson to confirm that he’s unarmed. Once the intruder gets close enough, Sherlock sprays him in the face with mace and then knocks him out.
John arrives home later and finds a sign on the door saying, “Crime in progress. Please disturb.” He goes upstairs and finds Neilson tied to a chair. Sherlock tells John to take Mrs. Hudson downstairs and look after her, and then calls Lestrade and tells him that they’ve had a burglar, and that the man fell out of a window.
In the kitchen, John tends to Mrs. Hudson’s injuries. Neilson falls past the kitchen window and hits the ground. The police arrive and take the injured Neilson away. Lestrade is clearly skeptical of Sherlock’s claim that Neilson fell out the window by accident but doesn’t pursue the matter. Sherlock goes back inside and insists that Mrs. Hudson can stay there, and then recovers the camera phone from her. She’s had it all along since she found it in Sherlock’s second best dressing gown.
The two men go back to their flat and John asks where his friend has hidden the camera phone. Sherlock tells him it’s where no one will ever look, and they figure that there’s more on it than just pictures. John asks how he feels about Irene being alive and asks if he’ll be seeing her again, but Sherlock simply plays Auld Lang Syne
as the clock strikes midnight.
Irene is walking down the street when she receives a text message from Sherlock wishing her a Happy New Year.
Later, Sherlock goes to the morgue and x-rays the camera phone while Molly looks on. She wonders if the camera phone belongs to his girlfriend, and Sherlock points out that it would be silly to x-ray his girlfriend’s camera phone. He gets an idea and enters 221B as the passcode, but it also fails, leaving two attempts.
Sherlock returns home and hears crying from his bedroom. John comes home and his friend tells him that they have a client: Irene. She tells them that there are people out to kill her but won’t say who, and asks for her camera phone. Sherlock claims that he put it in a safety deposit box, and John suggests that Molly give it and then have one of Sherlock’s homeless network members deliver it to them. However, Sherlock then reveals he has it and asks Irene what is on it. She tells them that she has items on it that she can use for “protection,” but Sherlock notes that she’s acquired something that’s more danger than protection. He asks her to show him what it is but when she refuses to give him the passcode, Sherlock hands it over to her. The passcode doesn’t work and Sherlock explains that he gave her a duplicate and now he has the passcode: 1058. However, when he enters the passcode into the real camera phone, it doesn’t work and Irene says that she knew it wasn’t her camera phone.
Irene finally explains that the camera phone has an email from a Minister of Defense who claimed it would save the world. It says “007 Confirmed Allocation” followed by a lengthy alphanumeric code sequence. He realizes that it’s the seating arrangement for a 747 going to Baltimore at 6:30 the next day from Heathrow. Irene says she’ll have sex with him on the desk until he begs for mercy twice, and Sherlock simply tells John to double-check the flight schedules and says he’s never begged for mercy. John mentions that it’s flight 007 and Sherlock realizes he’s heard that number before. Meanwhile, Irene secretly texts the flight number and departure time to Moriarty. Moriarty then sends a taunting message to Mycroft, who is stunned at the news.
Sherlock focusses on the 007 number and remembers that Mycroft spoke to someone on the phone about “Bond Air” and Coventry. When he snaps back to reality, he discovers that John has gone out and Irene is still there. He tells her that during World War II, the British authorities broke a German code message referring to the bombing of Coventry, but they let it happen so the Germans wouldn’t know their code was broken. Irene asks Sherlock if he’s ever had anyone and then invites him to dinner. She takes his hand and Sherlock asks why he would want dinner if he isn’t hungry. Irene asks if he would have dinner with her if it was the last night of the world. Before he can answer, Mrs. Hudson ushers in the man who picked up Sherlock earlier. The man, Plummer, gives him a ticket for Flight 007.
Sherlock leaves with Plummer and tells him that the British and Americans know that there’s a terrorist bomb on a passenger jet and will let it detonate rather than reveal they have an inside source. They arrive at Heathrow and pull up to a jet. Neilson is there, clearly unhappy to see Sherlock. Sherlock goes into the plane and discovers that the passenger seats are filled with corpses. Mycroft comes in and explains that they’ll send the plane up with the corpses, and it will appear authentic. He points out that several of Sherlock’s recent encounters have involved people who had missing relatives, and that the dead man who wasn’t on the German plane that blew up didn’t make his flight. However, Mycroft tells his brother that the terrorists know about the operation now because Sherlock showed off his solution to the email code to Irene, and Irene sent it to Moriarty.
Irene comes in as Mycroft apologizes for directing Sherlock to her. She dismisses Sherlock as irrelevant and tells Mycroft that she has a great deal more information on the camera phone, enough to bring down the British government. They go back to Mycroft’s office and Irene has Sherlock confirmed that the camera phone will self-destruct if anyone tampers with it. When Mycroft threatens to torture her for the passcode, Sherlock warns that there are two codes and that even if Irene gave up the information, they wouldn’t know which one and a second attempt would be impossible. Mycroft is willing to destroy it, but Irene points out that it might contain information that could save British lives. She gives Mycroft a list of demands and protections that she needs, and demands an immediate answer. Irene admits that Moriarty helped her by giving her advice on how to play Sherlock and Mycroft.
Mycroft congratulates Irene on playing the game, but Sherlock interrupts and says, “No.” He tells Irene that she got carried away and felt sentiment toward her. Irene insists that she felt nothing for him, but Sherlock says that he knows she had feelings for him because he took her pulse earlier when she held his hand at the flat. He picks up the camera phone and starts entering the code, telling Irene that she could have picked any random number, but she let her heart rule her head. Irene takes his hand and tells him that nothing she said was real and she was just playing the game. Sherlock tells her that it is a game, and she’s lost... and finishes punching in the correct code, SHER. He gives the camera phone to Mycroft and suggests that he let Irene go, since she won’t last long without protection. Irene begs, admitting that she won’t last six months, but Sherlock apologizes for dinner and leaves.
A few months later, John arrives at the flat and finds Mycroft standing outside the café below. They go inside and Mycroft tells John that the file on Irene is closed forever. He suggests that John tell Sherlock that Irene got herself into a witness protection plan in America and that Sherlock will never see her again. When John wonders why Sherlock would care, and will only call her “the woman,” Mycroft suggests that it’s a salute and that Irene was the one woman who mattered to him. They both figure that Sherlock will be fine, and Mycroft then says that he decided to tell his brother that story instead of the truth: Irene is dead, beheaded by terrorists two months ago. He pushes Irene’s file over to John and asks him what they should tell Sherlock.
Sherlock is working when John comes in and says that he has news about Irene. He hesitates and then tells Sherlock that she’s in America in the witness relocation program. When John points out that Sherlock won’t be able to see him again, Sherlock says that he has no interest in seeing her again. He does ask for the camera phone and won’t take no for an answer. John hands it over and starts to leave, but then asks if Irene ever texted him again. Sherlock tells him that she did, a few months ago, and said, “Goodbye, Mr. Holmes.” Once John leaves, Sherlock goes over all of the text messages that Irene sent him.
Two months earlier
Irene sends her last message to Sherlock and awaits her beheading. The executioner reveals that he’s a hooded Sherlock and tells her to run, and then swings at the terrorists.
Sherlock puts the camera phone in a drawer and smiles admiringly, saying, “The Woman.”