Mycroft's handler at MI6 asks Sherlock to investigate the death of a mentally disturbed operative. Watson tries to cope with her feelings about the kidnapping, as well as Mycroft's deceptions.
- "Elementary" - "Art in the Blood" - May 8, 2014
Holmes races to the precinct to enlist the captain's help to save Joan after being tasered by Mycroft. But then Joan calls her.
Sherlock returns home and sees Joan being tended to by a medic and she and Mycroft being watched over by two bodyguards.
Joan assures him she's fine. Mycroft says he can explain and Joan excuses herself saying she's heard this already and goes to bed.
Mycroft explains that he wasn't working for the French crime syndicate, in fact, he is an asset to MI-6, British intelligence and has been for 10 years. He can't believe Mycroft didn't tell him but Mycroft points out that they're not exactly close.
It turns out that Mycroft developed a keen observational eye for crime and storing facts through the restaurant came in contact with criminals like those in Le Milieu and MI-6 has been exploiting that. He didn't tell him the truth because he didn't want to blow his cover. (While telling his story in the kitchen Mycroft is handling a jar of something and Sherlock tells him to put it down because it's toxic mold he's using in an experiment.) He admits that a few months back he wanted to lure him out of New York on his handler's advice. They argue about Joan and her involvement, and Sherlock says it's going to take some time to process. Mycroft's handler asks to see them both.
They meet at a tony club and Mycroft seems annoyed when his handler Sharington takes a specific interest in Sherlock and his skills and asks him to take on a case. A former asset to MI-6 Arthur West has been murdered. He was once a great help but his bipolar disorder made him erratic and hard to believe. He recently got in touch about something and coincidentally died in a robbery gone wrong so if Sherlock looks into it, Sharington will consider Sherlock and MI-6 square for saving Joan's life.
Sherlock heads home and apologizes for everything Joan has been through and tries to talk about how hard it would be for him if anything ever happened to her. Joan cuts him off and says she's fine but not feeling like talking about it and is eager to have the work of a case to distract her.
They go to the autopsy to look at West's body and discover that his arms have been cut off, for no apparent reason. Someone busted in and took the arms and altered the surveillance system. Bell and Gregson come in and Sherlock claims they have no interest beyond the cold case thing they do from time to time as not to blow Mycroft's cover.
Sherlock and Bell go to talk to West's ex-wife Marian and Joan goes to West's house to investigate.
Sherlock and Bell talk with Marian and she admits that although she has a new boyfriend she has been continuing to care for Arthur because she cares about him and wanted to make sure he was alright with his meds and food so she lied to the police about seeing him. She has an alibi. Sherlock notices she's a tattoo artist and when he asks about whether Arthur had tattoos she evades. He knows she's lying.
He calls Joan and asks her to look around Arthur's apartment for supplies that are associated with caring for tattoos. He realizes that Arthur's tattoos--probably secrets he was trying to keep-- were invisible to the naked eye and only visible under UV light. Joan finds the items.
When she heads home she runs into Mycroft. She won't let him speak or apologize and says that no matter what he wanted to say that there is no possible future for them and anyone that could lie the way he did, so elaborately and for so long she would never be able to trust him and she doesn't want to see him ever again. She notes that Sherlock, for all his faults, may be too honest but she knows exactly where she stands and he deserves better than Mycroft and so does she. He says he understands.
Sherlock meets with Sharington and says his interest has been piqued by the Arthur West case and will keep working on it.
Sherlock and Joan meet at home and he tries to commiserate about Mycroft's deception saying Moriarty did the same to him. Joan says she does want to talk but not about that. And then the doorbell rings.
It's Marian, she says she's been under surveillance and thinks whoever killed Arthur is now after her and he told her she could trust Sherlock. She explains that she couldn't speak in front of the police but that Arthur was assigned to study Sherlock when he was working for MI-6 and he was very impressed with Sherlock and knew he was one of the good guys. Arthur also knew Mycroft was an asset. She brings them photographs of Arthur's arms under UV light, exposing the "secrets." It is some kind of code with letters and numbers. She says Arthur was convinced there was a mole in MI-6 and they were giving info to a spy in New York. She can't explain the numbers but hopes they can. The supposed spy's name was a man named Julian who owns a bookstore in Queen. Sherlock is skeptical but they give her a place to stay for the night and begin investigating the bookstore owner.
Joan tells Sherlock she's moving out. He tries to tie it to the Mycroft trauma and is very dismissive. She says she was already planning it. He puts it off and says the feeling's will pass and walks away testily. She says she loves what they do and their partnership but she needs a real life outside of this. He walks away silently, leaving the apartment.
The next morning he meets with Sharington again and asks about being spied on in London. Sharington says he should be flattered in a way. Sherlock tells him Arthur's mole in MI-6 theory and he thinks it's likely even though he can't work out the code on his arms. He asks if Sherlock will see the case through and asks him to come work for them, permanently and to imagine what he could do with MI-6's resources. Sherlock says Sharington and Mycroft have upturned his life enough and he's done.
Marian and Joan have breakfast and Joan tells her they've found her clean ID and a place to stay. Joan asks her about Mycroft. She explains that Mycroft had gotten out of MI-6 and gotten on with his life but something brought him back.
Sherlock is looking at cold cases at the precinct when Gregson shows him a ballistics report for the gun that shot West saying it was found but there were no hits on the prints which have a distinctive scar. Sherlock suddenly excuses himself.
Joan goes to see Mycroft and asks him to explain what happened. It turns out that he went back to work for MI-6 as a way to protect Sherlock, who, at the height of his drub abuse, worked unwittingly for a terrorist. Mycroft kept him out of jail by going back to the agency. Of course, Mycroft didn't tell Sherlock this or Joan. He didn't want to appear to be dodging blame or send Sherlock back down a bad road since he's more fragile than he seems. Mycroft says they share that, taking care of Sherlock whether he realizes it or not. Joan is so touched by this she sleeps with him. All is forgiven.
Sherlock rushes home, grabs the jar Mycroft had been handling, dusts it for prints and sees they match those found on the gun. He calls Sharington and tells him he has found his mole.
He busts in on Joan and Mycroft who are still in bed. He tells Mycroft he needs to skedaddle because someone is clearly framing him for murder and setting him up to look like the mole.