A woman is getting out of the shower when a man grabs her from behind. He's wearing a stocking and hauls her into the bedroom where they struggle. But then he starts to choke and she asks if she hurt him, then calls an ambulance for Bob…her husband.
House is having problems with his new roommate, Wilson, and tells him he's going to have to move out. At the hospital, Bob and her wife Maria are discussing his symptoms and their open sex life with Cameron, who is okay with it and bets against House that the couple is happily married. They start a barrage of treatment to diagnose why his threat is swollen.
Later House is meeting with a patient, Vincent, with urination problems but it turns out he has herpes. He denies he's only had sex with his wife but House is skeptical and provides treatment for Vincent…and his wife, and his daughter, and her karate sensei. Cameron asks Maria about their sexual role-playing and Maria admits there's only so long a married couple can keep things up without it.
The test come back revealing there's lung scarring and reduced capacity but there's no indication of the cause. House is confident there'll be more symptoms and sure enough, they get a page and find Bob is having a rash on his chest, driving him into uncontrollable scratching.
House and the staff are discussing Bob's symptoms and ruling out various possibilities – they wander into the restroom and Cameron has to come in as well. House concludes it might be a heavy-metal concentration and House orders tests and a search of their house. While House spars with Wilson over their home life and discovers he's an excellent cook, Foreman finds ants at the couple's house but the tests for heavy metals prove negative. House orders treatment for lead poisoning but also orders tests for food allergies. Bob continues to get worse, complaining of extreme foot pain, while Vincent's wife wants to file a complaint.
Bob goes into breathing arrest again and vomits and they have no choice but to trach him. Foreman insists it's lupus but House still believes it's heavy-metal poisoning, but they can't treat without knowing the specific metal. House continues to take advantage of Wilson's cooking skills while Cuddy confronts him about Bob's wife Maria. House gets an idea – Bob's wife Maria is responsible and is trying to kill him. House orders a search of the couple's house without Maria's knowledge then confronts her directly. She agrees to let him search her purse and he finds nothing. Cameron insists she's innocent and Cuddy refuses to let House give her a cavity search.
Undeterred, House watches Maria while Wilson goes on about his ongoing divorce. As they watch, Bob has another respiratory arrest and Foreman suspects a stroke. He revives and Maria wonders if he's wrong about her because of her concern and relief. House suspects the lupus treatment suppressed his bone marrow and left him open to a viral infection. House orders interferon treatment against the viral infection and Foreman warns Maria there could be side effects, but there's no choice.
Maria and Bob share a moment when he thinks he's dying, and House orders Foreman to increase the dosage. Then House meets with Vincent and his wife and reveals she has herpes but doesn't need an outbreak to spread the virus. When they fight, House suggests one of them might have got it from a public toilet, and when Vincent buys it he figures he's the one who had the affair. House sees their wedding ring and gets another idea – he orders a test for heavy-metal poisoning with gold and orders Cameron to keep Maria out of the bathrooms.
House goes to his house for a vital piece of information where he finds out that Wilson has taken pity on his maid, who was fired by his wife. She's rearranged House's closet and moved a chest that he's looking for. – He needs the bottle of stannous chloride that is in it. Maria insists on going to the bathroom over Cameron's objections just as House arrives. He goes into the bathroom after her and tells her that he'll recover. The bad news is that he didn't want her to wash her hands because she has a toxin on it that reacts to the stannous chloride. She's been using an uncommon arthritis medicine found in Mexico (where the couple took a trip) that has gold in it, and she sprinkled it on his cereal.
The staff is left to speculate why she might have tried to kill her, but they have no answer. Maria is taken away by the police and Bob starts to respond to the treatment. Cameron pays off on her bet. Foreman and Chase tell Bob what happened while House heads back to his apartment to take more of Wilson's food…and erase a message that there's an apartment available for Wilson.