Margaret McPherson is at home, alone, during a stormy night. She starts to hear noise around the house and panics, calling her husband Billy. Margaret looks around the house and finds a loose door, but no signs of an intruder. As she goes back downstairs, she jumps as Billy comes up behind her. He assures her that everything is okay, but Margaret complains of stomach pains and starts vomiting.
House wakes up in the morning and discovers that Cuddy has already left his bed and gone to work. When he arrives at work, he discovers that Chase has hired a new fellow, psychiatry resident Dr. Kelly Benedict. House notes that she's hot, and points out that looks like Cameron. He figures Chase hired her because he still has issues over his divorce with Cameron. Foreman and Taub would rather focus on Margaret's case, but House tells Kelly to do the differential. Foreman shoots down all of her suggestions and suggests hepatic fibrosis. Taub proposes lead poisoning, and House tells them to check for both.
Next, House goes to buy a new motorcycle and takes Wilson with him. He admits that it's his idea to have Cuddy go home at nights, and admits that he finds her daughter Rachel boring.
As they run tests, Chase assures Kelly that she's fine, and House is trying to test her. She notes that Foreman doesn't like her but Chase warns that he doesn't warm up easily. They find scar tissue and realize that she has had broken ribs in the past... and lied to them about it.
Foreman and Taub check the house for lead poisoning and Taub wonders why Foreman has a problem with Kelly, and suggests it might because she's replacing Hadley. Foreman insists that it's only temporary and he has no romantic feelings for Hadley. He finds a credit card receipt confirming she was in Trenton rather than Summit on the day she collapsed, even though she claims she was in Summit.
At the hospital, the team and Billy confront Margaret about her lies. She claims that she just forgot which day she worked in which town, and that she broke the ribs during a university biking accident ten years ago and didn't think it was important enough to mention. Margaret tells them where she had the ribs treated.
Cuddy is leaving House's apartment for the day so she can be home when her babysitter is done for the day. House tells her that his message therapist is coming, but Cuddy is surprised to see that the therapist is a scantily-clad woman.
Kelly confirms that Margaret lied about the biking incident, was never registered at the university, and is using a stolen Social Security Number. They're called to Margaret's room where she is having a seizure.
Afterward, House confronts Margaret and asks for the truth. She finally admits that she was married to a guy five years ago, and he abused her. Margaret got a restraining order and ran away, but he found her and broke her ribs. She escaped him, but later he tracked Margaret down and fed pesticides to her dog, killing it. She was in Trenton to meet with a support group for abused women. Billy demands to know what her ex-husband's name is, and she tells him it's Carl. She warns him not to confront Carl because he'll kill her.
Back in differential, House pulls up a chair and has Kelly meet with him one-on-one to present a diagnosis. She doesn't get anything right, and House suggests that maybe Carl caught up to her and poisoned her. Kelly doesn't believe it, noting that poison is impersonal, but House notes that the ex poisoned her dog. Foreman suggests that Margaret has pesticide poisoning and House orders the proper treatment.
In the elevator, Foreman accuses Chase of wanting to sleep with Kelly. He points out that Kelly had only middling grades, but Chase notes she was editor of the undergrad newspaper. Foreman warns that he decided she was the right candidate before putting her through a full interview.
Billy wonders why Margaret didn't tell him about Carl, but she insists it was the worst time in her life and wanted to block it out. In response, Billy walks away. Meanwhile, Cuddy asks House about the masseuse, Brandi, and he admits that she's a hooker. He also admits that he had sex with her, but not since he and Cuddy got together. House insists that Brandi is the best therapist he could find, and points out that she objects to the sex part even though it doesn't exist. She offers to find him a better therapist, and tells him that she won't see him until he stops seeing Brandi.
Kelly is crashing to study up on symptoms when Chase comes in and tells her to take a break. She points out that she wasn't the editor-in-chief, just an editor, and tells him it's okay if he reconsiders. Chase gets a page that Billy has been admitted to the ER.
House goes to see Wilson at his condo, and Wilson already knows about the hooker from Cuddy. Wilson tells him to give in even though House thinks it's irrational. When he advises House to get a gift and apologize, House immediately agrees and leaves.
Chase takes Kelly to the ER and suggests they determine if Billy has the same symptoms. It turns out that Billy was beaten up. He explains that he found the name of a guy called Carl in Margaret's address book. Billy confronted the guy and got beat up, and it turned out the guy was a co-worker, not Margaret's ex-husband. Foreman calls Chase to tell him that Margaret's fever has spiked, meaning it's not pesticide poisoning.
Back in differential, House prepares a slide projector and invites Kelly to stand up by the screen. He then projects a slide of young Dr. Chase with his mother... who looks a lot like Kelly. Foreman finally has enough and tells House to stop. Kelly suggests Legionnaire and notes there was an old air conditioner in the apartment. House agrees to test, but Foreman notes that Taub didn't write up the AC system. He did mention it to Chase, however, and they realize that Chase gave Kelly the idea.
Afterward, Chase wonders what Foreman is up to. Foreman insists that Kelly isn't qualified and it impedes him in particular. Chase notes that House had him hire the fellow, and Foreman resents it. When Foreman insists that he's in charge, Chase points out that he has no authority and that Foreman is taking on Kelly because he doesn't have the guts to take on House.
A man comes into Cuddy's office and introduces himself as Felipe, a masseuse. With some prompting from House's cue cards, Felipe convinces her to skip a meeting and get a massage. However, she soon discovers that Felipe has no idea what a masseur is. When she says that House is her boyfriend, Felipe admits he's surprised that a boyfriend would hire him for her, and Cuddy realizes that he's a prostitute.
Chase goes to see Kelly, who admits that Chase has turned her into a liar. He apologizes and Kelly suggests that she should quit because she's not like the rest of the team. Chase tells her to use her psychiatrist training to read Margaret. Kelly goes over Margaret's files and then talks to Billy. He explains that there's no support group for women at Trenton, and he wonders what else Margaret is lying about. Kelly assures him that Margaret is acting like an abused woman, and tells her not to put Margaret on the defensive.
Cuddy comes to see House about the male hooker. House claims it doesn't bother him, but Cuddy points out that a) she didn't have sex with him before, and b) Felipe is gay. House insists it's just a massage, but Cuddy points out that he must be trying to sabotage their relationship before it gets serious. In response, he notes that she hasn't let him into her home or introduced him to her daughter, Rachel. House admits that they can't become a couple if she hides Rachel, and Cuddy admits that if House gets too close and then leaves, it'll be a problem. House notes that she's also holding back.
As Billy tries to talk with Margaret, she starts hallucinating about slugs and flames.
House wakes up alone in bed.
Back in differential, House realizes that whatever Margaret has is in her brain. The only way to confirm any illness is a biopsy, but Kelly suggests they're not connected. She proposes that her delusions are consistent with bipolar disease. House derides her opinion, and Foreman comes to her defense. He insists that letting House pressure Kelly is going to mess her up. House backs up, while Chase nods his thanks to Foreman.
As Chase prepares to biopsy Margaret's skull, Taub stops him and explains that her temperature is back to normal, despite the fact she's been off the cooling blanket for an hour. Now they are missing a symptom. House wonders why Margaret wasn't chilled from the cooling blanket, and Kelly says that she slowly reduced power... which concealed the lack of fever. The team realizes that Margaret has stopped vomiting. House goes to see the patient and turns off the pacemaker, and they realize that her heart has stabilized on its own. That leaves the delusions, and Kelly insists it's a biopolar disorder, prompted by the physical symptoms. House gets an epiphany and tells Kelly that she's got it wrong. He orders the team to give her two specific drugs and wait a few hours for them to kick in.
A few hours later, Margaret is rational and manages to overcome her delusions. House explains that she lied because she thought she would be cured. She was in Trenton seeing a doctor who gave her risperidone... for schizophrenia. Margaret was never married, and she was out on the streets when her ribs were broken. All of the symptoms were side effects of the risperidone treatment. Margaret admits the truth, much to her husband's shock. As House goes, he points out to Kelly that she should have figured it out.
Later, Billy asks House what he's supposed to do. House tells him that she can take a different anti-psychotic, but Billy doesn't know if he can stay with a woman he doesn't truly know. House points out that his wife has a serious medical illness and Billy admits that it's hard... and House says that it's always hard. As he goes, Chase catches up to him in the elevator and admits that he was wrong about Kelly. House leaves it up to him, saying that Kelly gave him the idea that solved the case, which is more than the rest of them did. Chase says that he will, and House tells him that it'll be easier for him to sleep with Kelly if he does.
Billy goes in to see Margaret and comfort her.
Cuddy finds House in her office looking for porn on her computer. He tells her that he's giving up Brandi, and she invites him to stay at her place.
Chase discovers that Kelly is packing to leave. She figures that House has fired her, but tells Chase that it's good because she doesn't date men that she works with. Chase decides to fire her and then invites her to dinner.
House and Cuddy enjoy dinner with Rachel... who chews on House's cane. He has to admit that she's adorable.