Keith Foster and his girlfriend Pam are making out in his bed and she suggests they do it. He reluctantly agrees and she gets his car keys from the nightstand. They go driving in his father's Porsche with Pam at the wheel, and Keith starts coughing uncontrollably. Pam finally realizes something is wrong when he coughs up blood. Distracted, she spins through an intersection beneath a truck and misses, but a bus slams into them.
Later, Keith is taken to the hospital and his father and Pam sit at his bedside. Meanwhile, House confronts the pharmacist because the shipment of Vicodin has been delayed for an hour. Cameron brings him Keith's case and notes he's had internal bleeding for three hours. House is more interested getting Cuddy to get the Vicodin in, but she has no better luck than he did. Cameron finally gets his attention when she explains that Keith has hemolytic anemia and there's no explanation. Intrigued, House calls his team together but is distracted by the pain in his leg. Foreman thinks it's environmental, but House notes Keith will get better now that he's out of his house. The team disagrees and House tells them to check out their individual diagnoses while he goes to the pharmacist.
Cuddy notices House picking up his Vicodin and goes to confront him. She accuses him of being an addict in denial, and warns that she can't always protect him. When House denies that he has a problem, Cuddy offers to give him a month off of clinic duty if he goes drug-free for a week, and House agrees.
Cameron asks Mr. Foster if Keith is doing drugs, which could account for his symptoms. Mr. Foster notes that Pam was in rehab in the ninth grade and is supposedly clean, and confirms that his wife died of cancer. Chase takes hair samples to test for drugs and it turns up negative. They also check for infection, while Cameron asks Mr. Foster if anyone in the family has had lupus. Mr. Foster says that they haven't, and admits that he doesn't know what is going on in Keith's life. She then confirms that Keith's mother had pancreatic cancer, and Wilson checks for lymphoma. As Wilson works, Keith worries that he had cancer. When Wilson says that they're just testing, Keith notes that's what they told his mother.
The team reports that everything has tested negative, and that Keith's condition is getting worse. Foreman notices that House is looking distressed, but they are interrupted when Keith complains of something in his left eye. They don't find anything, but Keith quickly goes blind. They find a retinal clot in the left eye, but can't use blood thinners. However, if they don't fix it in two hours, he'll lose his eyes. A fatigued House calls for differential, and is surprised that Wilson is there. He figures Wilson is there to make sure he's abiding by the bet, and insists that he's fine. Wilson finally tells the team that House is going off the Vicodin. When Foreman warns that he'll go through withdrawal, House insists that he won't because he isn't addicted. He focuses on the case and the team concludes that it's an infection in the heart, and the clot went from there to the eye. House is distracted by an attractive woman stretching outside before jogging, and tells them to test.
They confirm that the woman is Ingrid, a masseuse who doesn't speak English. However, she applies pressure to House's hand and relieves his pain. Ingrid then tells him to take off his clothes.
As Chase checks Keith for heart infection, he admits that the blindness will be permanent.
Ingrid leaves House's office as Chase arrives to report that there's no sign of infection and the antibiotics aren't doing anything. House tells him to double the dosage despite the fact that it could cause kidney damage, and Chase suggests they remove vitreous fluid from the eye to make the artery expand and let the cot move. House is impressed and tells him to do it, but as soon as he's alone he staggers against the wall.
Chase performs the operation and Keith regains his eyesight. Afterward, Pam comes to see Keith and blames herself, and worries that Mr. Foster hates her. Keith tries to reassure her, but starts vomiting. As they take him to the ICU, Chase figures that it's the double dose of antibiotics, while Mr. Foster accuses Pam of giving his son drugs. House insists that it's kidney shutdown. When Mr. Foster takes offense, House insults him and Foreman hastily separates them. As the others leave, Cameron notes that House overreacted and he agrees. She asks if proving Cuddy wrong is worth the pain and walks off.
The team meets and waits for House. Foreman insists that House should be removed, while Cameron defends her boss. House arrives and tells them to focus on their case, not him. Cameron still believes that it's lupus, but House notes it's moving too fast and suggests Hepatitis E. He admits that lupus is more likely, but they still need to test for Hep E. He orders treatment for Hep E, explaining that it will hurt Keith, but just enough that they can confirm he has it. When the team points out that Mr. Foster won't go for it, House tells her to lie to him because he trusts her. As she leaves with Foreman and Chase, Cameron insists that she doesn't want to lie. Foreman tells her to treat for lupus, but Chase warns that doing so will get her fired. Chase figures that House knows what he's doing, but Foreman thinks he's delaying treatment because he's not rationale due to the pain.
A seriously strung-out House is in his office and takes a pestle. After a few seconds he slams it into his hand and then smiles in relief.
Cameron lies to Mr. Foster, but he wonders why they are treating for Hep E if they haven't detected it. He talks about how the doctors offered an experimental treatment for his wife, but it shortened her life. Cameron then tells him that she thinks that it's lupus.
Wilson checks House's x-ray and asks how he broke his hand. He realizes what House did and why, and House admits that he's feeling better. Cuddy comes in and asks why House told Cameron to lie. He doesn't try to defend himself, and Cuddy warns that Mr. Foster is angry and insisting on the lupus treatment. She tells House to take a break for a week, but House refuses and insists that taking the risk is more likely to save Keith. Cameron comes in and tells them that Mr. Foster wanted to move Keith to another hospital, but caved when she warned him that Keith was too unstable to be moved. Mr. Foster agreed to do it House’s way, much to his satisfaction.
Cameron and Chase prepare to administer the treatment, and Keith starts hallucinating before they can begin. He mutters that someone named Jules is attacking him, and then snaps out of it. However, they realize that he's suffering from rectal bleeding. Keith passes out as Cameron calls in a team. An angiogram reveals major intestinal bleeding and liver failing. That and the hallucinations convince Cameron that it's lupus. House is more interested in learning who Jules is, and notes that it takes years for lupus to develop. Cameron blames House for delaying the treatment, costing Keith his liver. House points out that she's angry because she had to lie, and because she made the mistake of trusting him. He still insists that lupus is a bad diagnosis, but the team insists that it's the only diagnosis they have. House tells them to put Keith on the transplant list and notify Cuddy so she can get him to the top. Once the meeting breaks up, Foreman follows House into his office where he's vomiting into a wastebasket. He insists that his boss is going through withdrawal, and gives him Vicodin so he doesn't have to cover for him, and so House won't kill his patient. Once Foreman leaves, House opens the bottle and picks up a pill.
Cameron explains what is happening, and Mr. Foster figures that House endangered his son. Cameron admits that he's right and apologizes.
Cuddy tells Foreman that she can't do anything to get Keith moved up on the transplant list.
Mr. Foster offers to volunteer his liver, but he's the wrong blood type. House arrives and asks him who Jules is. Mr. Foster explains that it's the name of their cat, and House insists that it's a psychosis relating to something real, not a hallucinatory fantasy. thus disproving Cameron's theory of lupus. The father says that Jules died, and House points out that it's critical to know the complete medical history. House pushes the issue, asking how the cat died, and Pam says that it died of old age. When he learns that Jules slept in Kevin's bed, he sends Chase and Foreman to dig it up. House then dissects the cat, and Cameron watches as his hand shakes.
Cuddy arranges for Keith to receive the liver and escorts it into the hospital. Meanwhile, House finishes his dissection and goes to the operating room just as Dr. Hourani prepares to remove Keith's liver. He tells them to stop because he's confirmed that Keith has acute naphthalene toxicity. The Foster home had termites, and they extruded naphthalene in their nests. When Hourani doesn't believe him, House coughs on him and then starts sneezing on Keith. The surgeon has no choice but to call off the operation.
House's team confronts him and insists on going ahead with the surgery. When they point out that Keith hasn't gotten better when removed from the home, House explains that naphthalene is a gas that is fat soluble. It was stored in his fat cells, but when Keith lost weight due to the bad hospital food, the naphthalene poured into his system. Cuddy and Mr. Foster arrive, and Mr. Foster slugs House. House explains that the cat died of acute liver failure and internal bleeding, just like Keith is. He asks for 24 hours to feed Keith and build up his fat reserves. Mr. Foster wonders if he's guessing, but House insists that if they do the surgery, Keith will die. The father turns to Cameron, who says he should trust House, and then he agrees to give up the liver and wait.
Chase and Foreman go to the home and break down the wall, and find termite nests.
Forty-eight hours later, Keith recovers and his liver heals. Cameron leaves them alone as Mr. Foster hugs his son and takes Pam's hand.
The week is up and House boasts to Wilson that he did it easy. When Wilson asks if he learned anything, House admits that he's an addict... but it's not a problem. He functions fine, but Wilson notes that he's changed since he's been taking Vicodin. House says that he's in pain and the pills take it away, letting him do his job.
Later, Cuddy comes to see Wilson, who explains what House said. He wonders if House is right, and Cuddy warns that House won't be happy if he finds out that the bet was his idea. Wilson figures that House will never believe it.
House relaxes in his office.