Gregson brings Bell to Holmes. The murdered family got threatening e-mails from Julian Walsh, a kitchen contractor who was fired a few weeks earlier. And he once did time for weapons possession and assault. So, you know. Worth checking out, right?
Mr. Walsh admits sending the emails, but denies killing anybody. And where was he between six and midnight? Watching television, he says. Holmes inspects the house and wonders if there's a basement because Walsh keeps glancing at the floor. So he asks where the bathroom is and goes downstairs, not upstairs. He finds a locked metal cabinet and a doorknob that's not attached to anything. Behind the cabinet, there's a room and a foreign-sounding scared woman's voice. Holmes busts in and there's a woman in underwear, handcuffed to a pipe. Holmes says, "Polizei" and she breaks down. Walsh is quickly under arrest.
Watson has gone to the rehab facility Holmes was at. It's nice! And she's talking to the man who had him for therapy for two hours a day for six months. He says, "I don't believe I learned a single significant thing about him." You'd think he'd mention that he's not allowed to talk to her about what happened in therapy, but I guess he wanted to skip straight to the part where he didn't learn anything.
The woman from Walsh's basement is being bundled into an ambulance. She's quite broken up about the whole thing. Holmes reports that she's a Russian prostitute named Katya who was sold to Julian Walsh. Walsh has been sleeping in her room. Bell is unhappy that Walsh's sex slave is his alibi. Gregson still doesn't want to follow up on Wade Crewes.
The morgue. Holmes is going to eyeball the slug that came out of the recent murder victims to compare it with the old case. He claims the eye is a precision instrument, so he doesn't need whatever ballistics computers would normally be involved. And based on that, he declares the grooves on this bullet to be the same as the old one, proving that it was the same murder weapon: "This is no longer a theory, captain. This is a fact. These cases are indelibly linked.