The big issue is that Watson's contract to nurse Holmes through recovery is almost up. Holmes doesn't think she'll really leave, and neither do any of the viewers. But even though Holmes offers up an assortment of ways for Watson to stay on as his apprentice, she ends the episode saying she's got a new client next week.
In the actual case, a woman named Terry Purcell is found dead in a hotel's industrial washing machine. She was the general manager of the hotel, but there are no physical clues on the body, what with the washing machine. Her office shows evidence of her being a kind, charitable person. So much so that Holmes naturally assumes that she was hiding something dark.
The first suspect is her husband Oliver, who has been sleeping on the couch, but he's got an alibi. Their daughter Carly is broken up about this whole thing. A gossipy neighbor sends suspicion toward Jeffrey Silver, who administrates a charity that Terry and Oliver volunteered for. He also has an alibi.
The next clue is that Terry had been threatened after shooing prostitutes out of her hotel. Further investigation reveals that she actually welcomed the prostitute trade, sneaking them in the back door and setting them up with diplomats without asking for a cut of the proceeds. Holmes eventually establishes that the real plan was to record the diplomats in their non-prostitutional endeavors. Because Terry Purcell was a Russian spy! And so was her husband Oliver!
Carly tearfully confesses that when she found out her parents were spies who were grooming her for a life as a deep-cover sleeper agent, she knocked her mother down and killed her. This makes Watson sad, so she investigates further, and she and Holmes establish that Jeffrey Silver was the handler of the Purcells, and he actually murdered Terry himself so he could keep Carly as a spy. So Carly's free! Although she doesn't get her soccer scholarship to Michigan, as she and Oliver have to go into witness protection.
Watson rushes into the kitchen where a teapot is whistling. Her banter with Holmes establishes that they've reached some sort of domestic equilibrium, and also that she is vexed about there not being any clean dishes. Surely someone who works with drug addicts must be used to dealing with bad housekeeping. She's leaving him in ten days, although we all know perfectly well that she isn't. Holmes claims that his messy kitchen means that he has an active mind.
Next, we cut to a completely different place. Two maids bicker about some missing yogurt and one of them goes to deal with an unbalanced washing machine. There's a dead body in there with the sheets! This scene was just like a Law & Order opening.
Once we get past the opening credits, Gregson tells Bell, Holmes, and Watson that the dead lady was Terry Purcell, the General Manager of the hotel. She appeared to have been killed by blunt force and then stuffed in the washing machine to get rid of evidence. Well, that's logical. There are no fingerprints to go on and no witnesses. Holmes finds a pen that was in the machine. It was broken in half but there was no ink on the victim or the sheets. Everybody kind of shrugs at this news. The security cameras have been broken for months, which Holmes says is proof that the murderer knew it was a safe place. And there are maroon streaks on the floor showing that the victim was dragged here from somewhere else. Holmes gets us out of the scene by asking, "You mentioned an office?"
I'm not sure Gregson did mention an office, actually, but they go there anyway. There's some blood on the corner of the desk. Holmes observes that the motive of the murder doesn't seem to have been theft, since the place hasn't been turned upside down. Watson points out that the walls are lined with charity awards, so Holmes concludes that Terry wanted to be acknowledged to be altruistic. He has already decided she was a bad person. Bell says she had a wedding band, so the husband is suspect number one. Let's go bother him!
The Purcells lived in an exceedingly suburban neighborhood, which will eventually be revealed to be Westchester. Holmes and Watson take a break from the case to talk about whether Holmes needs structure in his life. Holmes claims to be excelling at recovery, which means that Watson is tearing him down because she's annoyed by his success. He suggests a weekly salon in which he can share his wisdom in exchange for housekeeping. He's just assuming that Watson is looking for an excuse to stay with him, which is annoying her. But he's clearly right.