House is trying to get out of lecturing a class of medical students. He finally agrees to it after much complaining to Cuddy and an offer of two hours off clinic duty.
On his way to the class, House is stopped by a woman from his past named Stacy. She needs his help with a case and presents him with her husband's file. This catches House off guard -- he didn't know she was married. House thinks the diagnosis is something simple like indigestion or a kidney stone.
Stacy presses House for an answer. Her husband is suffering from abdominal pain and fainting, but three different doctors have found nothing. She begs for help, but House dispassionately responds that he isn't sure he wants her husband to live.
House lectures to a group of third-year medical students and presents three fictional patients, all of whom are complaining of leg pain. One will end up in a coma. The students make guesses about the diagnoses, and House walks them through his typical approach: never trust patients, investigate for yourself and don't care too much about them. He also interjects that sometimes you'll be completely wrong and will nearly kill a patient.
During a coffee break, House discusses Stacy's dilemma with Wilson. Wilson believes that something must really be wrong with the husband because Stacy is desperate enough to seek out House. He didn't think she'd ever get married.
The students interrupt the chat and pull House back into the lecture. They throw out more guesses to treat the three cases, and House continues to change the circumstances on them. Using an example of a farmer bitten by a snake, House explains his normal routine.
First, you find the type of snake and administer antivenin. If the patient has a reaction to that, figure out the other snakes it could have been. Who looks for the exact snake in the field and who simply administers other kinds of antivenin? Half the class goes for each option. House tells them that half of the class has saved the patient. The other half killed him.
House continues to pepper the students with details about each patient. One treatment works, the other doesn't. One patient isn't responding to treatment, another is possibly a drug addict looking for a fix. The students dutifully scribble notes and offer suggestions.
House turns back to the farmer. After telling the man that he is going to die from the snake bite, the farmer asks what will happen to his dog. The farmer's dog bit him, not a snake.
Moving on, the supposed drug addict is now discharging urine that has a brown tinge and is laced with blood. What could this be? His kidneys are shutting down due to muscle death, which releases myoglobin and is toxic to the kidneys. But, since all of the students prescribed antibiotics and bed rest, that patient will die in three days. They screwed up and killed someone, which is something they'll need to learn to deal with.
In the last case study, the patient is a high school volleyball player with tendonitis. A closer exam showed a nodule in the girl's neck. An MRI then revealed an osteosarcoma, which is a cancerous tumor in the femur. It has to be removed surgically, but if it's too large or too ingrained they may have to amputate the leg.
Coincidentally, the farmer contracted flesh-eating bacteria from the dog's mouth. The damaged tissue has to be removed from the farmer's leg and this procedure could also end in amputation.
In a hospital room, Cuddy tells a man in his late 30s that an MRI showed a problem and they may need to amputate his leg. Back in the classroom, Cameron, Foreman and Chase are observing House's lecture from the back row. As House explains that an MRI showed that the leg pain was caused by a clotted aneurysm that led to an infarction, the doctors realize that the three fictional patients in the lecture are actually one real patient -- House himself.
Flashback to the hospital room, where Cuddy tries to convince the man that surgery is necessary. The man is House. He refuses to allow them to amputate his leg, even with Stacy at his bedside urging him to allow the surgery. In the lecture hall, the empty seats begin to fill up. House explains that amputation protects doctors. If they cut off as much tissue as possible, they minimize the chance of something going wrong.
In the flashback, House demands no surgery. He wants them to try a bypass to restore the circulation. Stacy can't believe he's being so stubborn. House's surgery goes well, with a catheter drilling through the clot. As promised, the post-op pain is excruciating, caused by the muscle cell death.
In bed, House is looking through his own chart. He doesn't like how his potassium level is rising. He calls a nurse in and demands a dose of calcium glucinate. Before she does so, he goes into cardiac arrest. Cuddy rushes into the room to shock House back to life.
Back to present day. House explains to the lecture hall that the patient was technically dead for over a minute. House flashes to the time when he was under. He sees the farmer and the volleyball player now wearing prosthetics.
From the back of the class, Wilson asks if House thinks the dead patient's visions were real. House thinks the white light is simply a chemical reaction that takes place while the brain shuts down. Foreman and Cameron ask why he'd believe that and not something else. House replies that it's more comforting to believe that life simply isn't a test.
In flashback, Stacy is by House's bed as he struggles with the pain. She urges him to allow the amputation. He insists that he can get through this. If he had a patient of his own in this situation, he'd browbeat them until they accepted the surgery. So why is he resisting?
Stacy tells Cuddy that House has asked to be put into a chemically-induced coma so he can sleep through the pain. Cuddy says this is possible. Stacy comes up with a plan. Since she is House's medical proxy and he is unconscious, then she gets to make the decisions. Cuddy agrees to this, but isn't sure that's the right tack.
Cuddy puts House under. Stacy then asks Cuddy about the middle ground between a bypass and the amputation that she recommended earlier. Cuddy explains that they can go in and take out the dead muscle tissue. There's some risk of reperfusion injury, but Stacy quickly agrees to the procedure.
In class, House explains to the students that because so much muscle was removed, the utility of the patient's leg was severely compromised. Since they waited so long for the procedure, the patient continues to experience chronic pain.
The students begin to debate Stacy's proxy rights and her decision. House wonders aloud when the class is finished. Cuddy, who's been quietly listening in, answers that it was twenty minutes ago. House limps out.
Back in his office, House calls Stacy and leaves a message. He'll see her husband the next morning.