Remember Moriarty? She's played by Natalie Dormer and she used to pose as Irene Adler, the love of Sherlock's life? Well, Holmes has been exchanging letters with her as she sits in prison. We learn about this just in time for a case to come up that might involve her. A girl has been kidnapped, and Holmes recognizes the voice demanding the ransom as the man who posed as Moriarty. He tries out the name "Fauxriarty," but I hope we're all mature enough not to stoop to that.
Because the kidnapping was done by one of her lieutenants, Holmes is confident that it's a Moriarty operation. He and Watson visit her in her spacious warehouse cell, where she has occupied her time by painting a giant portrait of Watson's face. Weird! She offers to help out with the investigation if she can have some unspecified prison favors, but that quickly turns into her being brought to the police station so she "help with the investigation." She provides sketches of the men who seem to have done the kidnapping, but Holmes doesn't trust her.
Watson and Moriarty go back to the site of the kidnapping so they can say mean things to each other. Moriarty thinks Holmes is only hanging around Watson so he can figure her out. When they come back to the police station, there's a call from the kidnapper, and the kidnapped girl gets to plead for her mommy. Holmes continues to be angry at Moriarty's presence, because he can't figure out his own feelings for her.
Holmes determines that Moriarty's sketches conceal a numerical code. And two policemen get killed by Moriarty's lieutenant, who steals a phone so he can read an email and see the sketch for himself. This gets Moriarty sent back to her ultra-secure warehouse prison, but she escapes by gouging her wrists with broken glass and strangling her jailer. She goes straight to the bad guy's hideout and shoots everyone dead, because it turns out that she was the kidnapped girl's mother! It was all a scheme by the lieutenant to get some GPS coordinates from Moriarty. She surrenders to Holmes because she figures she'll be free in a year through legitimate means anyway. At the end, Holmes considers burning his letters from Moriarty, but he doesn't. It's kind of touching!
The previouslies involve Moriarty, who was also Irene Adler, Sherlock's one true love, whose (faked) death sent him into the drug binge that led to the start of this series. I believe that means we'll be seeing Natalie Dormer again tonight. Hooray! She's a lot of fun.
At the brownstone, Watson announces that she's going on a date with someone from her dating website. Holmes is wearing his beekeeping suit, but he denies being out of clean laundry. In fact, once Watson is gone, he goes up to the roof to spray things on his hives. And then he takes out one of the combs, inside which he has concealed a sheaf of letters. He probably has easier places to hide things, but it's just more fun to hide things in a beehive, you know?
The letters are from Moriarty, of course. Holmes writes her a letter by hand in which he wonders if he's really getting a response from her. He seems a bit contemptuous of Watson's "series of curated mating rituals," although he admits that "love, for lack of a better word, is a game I fail to understand." As he writes, we see the other members of the cast: Watson on her date, Gregson being sad about his marriage, Bell at the shooting range. His hand is still shaking, and he doesn't shoot. Holmes continues: "I find you a challenge. One that in spite of all that you've done continues to sitmulate." We see Moriarty. If she's still in prison, it's an awfully large cell. She's painted a portrait of Watson that's just enormous.
We also see people in all black with night-vision goggles coming out of a van and breaking into a building. Once they're inside, they spread out, find a man on the stairs, and shoot him. These night vision goggles are unnecessary, in my opinion, because it's not pitch black in here. A young girl is woken up, then covered with a blanket.
The next morning, the team is on the case. Gregson says the dead man was Max Fuller, a British national. Holmes says his ancestors built the railroad form London to Manchester. That's exactly the sort of meaningless trivia you can't stop yourself from saying if you know it. Mrs. Fuller woke up an hour after the invasion and found the body. There was no kidnapping note. Holmes would like to see the bedroom. But first, the phone rings, and the Caller ID is a question mark. Oh! It's the Riddler! Mrs. Fuller takes the call on speakerphone, and a smug British voice asks the other people on the scene to announce themselves. Gregson does, but no one else chimes in. The voice declares, "The price for the safe return of Kayden Fuller is fifty million dollars." Holmes recognizes the voice as the man who pretended to be Moriarty. He informs Gregson that Moriarty must be responsible, so he'd like to go talk to her. Even though she's in a SuperMax prison. Watson asks how he knows he's on her list of visitors.