Here's Holmes's defense of messing with Watson's private affairs: "I'll keep my secrets, you keep yours. If I'm still sober in five weeks, we'll go our separate ways." So he's ticked off about her finding his violin. Gregson calls. A search of Rebecca's place turned up nothing, and security cameras show her not leaving on the night of either murder. So she's off the hook. Also, nobody mentions this but it seems like if you're going to put on a disguise to commit a crime, the last disguise in the world you'll pick would be your own twin. Like, that's just going out of your way to mildly inconvenience the police. You'll still get caught, and the police will just be annoyed at having gone to the wrong place first.
Another rehab meeting. Holmes is whining to Watson about how he has to spend 45 minutes in the meeting. Instead of listening, which is what he's supposed to be doing. I wonder what he says when it's his turn to talk. He still thinks Rebecca did it. Watson brought a tack to poke him with if he trances out. I like that it's a trick she learned from Holmes! A woman comes up to talk about her addiction. Holmes pretends to be playing a violin. The world's smallest one. The woman says she met a doctor with three beautiful daughters and eventually his wife called the police. Holmes looks like he has an idea. Holmes and Watson leave. Watson insists on knowing what his breakthrough was. Holmes wants to find Rebecca immediately. Immediately!
Holmes enters Yvette's hospital room, where Rebecca's reading a book to her sister. He announces that he knows about Mary Margaret Phelps, the third heir. He shouts a specific address and that he's going to be her personal bodyguard. He's making a scene, and various people throng in, including Detective Bell. Bell drags Holmes away. Or he tries to, but Holmes throws him to the floor. So he gets handcuffed and dragged away to jail for assaulting an officer.
Ms. Phelps comes home and the camera follows her as she does various mundane getting-home things. Someone picks the lock of her front door. She gets a frozen dinner and puts it in the microwave while reading the newspaper. The intruder (who is a woman) pulls out a gun and sneaks in. She's stopped by police. "Put the gun down, Miss Thompson. Or do you prefer...Yvette?"
Watson explainsto Rebecca that Yvette was in a medically-induced coma, which she entered and left when her doctor gave her the relevant drugs. Holmes noticed that the doctor had a tan line where he used to wear a ring. Holmes goes over the whole story at length so we can see it happening. Watson says the "suicide attempt" was barbiturates, which simulate a coma. Yvette was seated for the murders because she was weak from drugs and the coma. Holmes further explains that his scene at the hospital room was a trap and that Ms. Phelps wasn't really a lost heir. Yeah, obviously. I don't know why they didn't just stake out the hallway outside Yvette's room. Or, for that matter, why the doctor couldn't have taken care of this murder on his own. Eventually, you have to stop relying on the woozy, drug-addled, recently-comatose woman, right?