A woman enters her house, apparently after going for a run. I deduced that from the running clothes she's wearing! And from the water she's drinking. A man knocks on the door and asks to use her phone because he needs to deliver some tables and chairs. He's got a cellphone and he needs to charge it up. She won't do it. She offers to call for him, but he can't remember the number. Disgusted, he leaves. And then she's grabbed by someone inside the house! He appears to use chloroform. Then he unzips a large rolling suitcase next to her unconscious body.
Outside, the delivery man thanks a cab driver for letting him charge his cellphone. In the background, a man pulling a large rolling suitcase goes past. In voiceover (that changes to in-person), Holmes explains that a man dropped his walking stick to pick up a mongoose. The man was a magician and this is all terribly elaborate. He's showing off for his recovery group. He ends with, "Again, my name is Sherlock and I'm an addict."
The story Holmes was telling is "The Adventure of the Crooked Man," the Arthur Conan Doyle story where Sherlock Holmes comes closest to saying, "Elementary, my dear Watson." Actually, he only says "Elementary," but he does say it to Watson. I approve of the occasional nods to Doyle.
Holmes and Watson come home, and Watson complains that Holmes is supposed to talk about his addiction, not his ridiculous life story. As Watson enters her home, a naked man comes out of the shower. Holmes comes up and calls him "Rhys." Rhys says that Emily has been kidnapped, and they got a ransom demand via video. Watson requests that Rhys put on some clothes, but she's a little put out when he enters her bedroom to do it. Holmes fills in the backstory: Emily is Rhys's daughter, and Rhys is Holmes's former drug dealer.
In the kitchen, Holmes makes tea. He also tells Watson that Rhys stayed in Watson's room. And he's an ex-dealer. Watson busts out the title of the episode, calling him "a giant gun filled with drugs, pointed at you." If that weren't the real title of the episode, I'd totally make it my fake one. Rhys comes down, and Holmes tells him he's sober and that Watson is here to keep him that way. Rhys accepts this.