Henry Arrington plays bridge with his friends when his daughter Amy gets up because she feels nauseous. Henry goes to help her but stops as electrical signals flash wildly in his brain. He stands still, maintaining an iron grip on Amy's arm. Moments later, he becomes conscious but is completely unaware of what just happened.
At the hospital, Foreman explains to Henry that he had an absence seizure. Foreman inquires about his recent history, but there is nothing out of the ordinary. Henry asks Amy to get him some coffee from the cafeteria. When she leaves, Henry shows Foreman something.
Foreman reports to the group that Henry's right testicle is twice the size of his left. Chase assumes it is testicular cancer, but House disagrees. Henry's MRI is clean. House points to a micro-abscess in the brain, which Foreman dismisses as a shadow. House thinks it could be an infection and he orders treatment for syphilis, gonorrhea and Chlamydia despite the fact that tests for all three already proved negative.
With the team perplexed, House explains that it could be lymphoma. Yet if it has already advanced to his brain and genitals, then it is too late. They can only treat for sexually transmitted diseases and hope that's all there is. When Foreman tells Henry that they suspect an STD, Henry claims he hasn't had sex since his divorce. He sticks to this story.
House thinks Henry is lying. He wants Foreman to interrogate him again after his daughter has left the room. Henry later explains that he couldn't admit the truth in front of Amy because he slept with her mother. His ex-wife had two affairs and Henry forgave her both times. Amy blames Henry for being an idiot and taking her back. Henry begins laughing, which causes him to cough up bloody foam. House calls for the crash cart as Henry struggles to breathe. It's definitely not an STD.
Chase points out that the problem is in Henry's heart, with vegetations obstructing the mitral valve. However, lymphoma wouldn't erupt so suddenly. House circles "acid reflux" on the white board. Henry mentioned that he had reconnected with his wife at a cheese tasting party.
House asks Henry about the cheese at the party and whether it was soft or sheep cheese. He feeds Henry a piece of cheese. Henry says it tastes similar to the one he had, and House reveals that it is regular American cheese with bacteria in it. Bacteria present in unpasteurized cheese can cause brucellosis. The antacid Henry was taking for acid reflux made his digestive tract an inviting environment for the bacteria. House starts him on a prescription of rifampin and doxycycline.
House admits to Wilson that, if he's right about the bacteria but didn't catch it in time, Henry will lapse into cardiac arrest. Henry does, and Chase shocks him back to life. He is able to restart the heart but not without significant damage. The patient did suffer from brucellosis but a vegetation broke off into his main coronary. Foreman gives him one week to live. With healthy brain and testicles, Henry now only needs a heart transplant.
House goes before the transplant board to plead Henry's case. The board is concerned about Henry's advanced age and they deny him the organ. Foreman breaks the bad news to Henry. Cameron comes to House with a letter of appeal she's writing to the board. Although House actually agrees with the ruling, he signs the letter anyway.
Cameron later comes back to House with patient files because she is searching for potential donors. The only possibility is a woman in her forties named Laura who was in a recent car accident. Yet Laura is still technically alive. She's also overweight, which means her heart isn't in the best condition. House considers this as being in their favor. Since most hearts with imperfections are thrown out, House may be able to salvage this one.
After Laura is pronounced dead, House sneakily reads her file. Laura's organs were declared not viable, and House prepares to search the trash. Foreman chases him down to tell him that Laura had hepatitis C. An infected heart will kill Henry in his condition. House doesn't believe it.
Laura's husband Donald gives the signal to take his wife off life support. House turns the machine back on because he wants to talk about the heart some more. House passionately makes his case to Cuddy. Even though Laura's heart was rejected, House can find a team to pull the surgery off. Donald angrily rejects House's pleas. As Donald storms out, Amy catches him in the hallway and thanks him for the heart he is giving to her father. Donald begins to crack, but when he sees House, his resolve stands. House would rather have Donald mad at him instead of the girl. Donald punches House in the groin as hard as he can. He tells Amy that he will donate his wife's heart to Henry.
The team tries to talk House out of the procedure because Laura's heart is too damaged. House intends to cure Laura's problems first before using the heart. They run through various diagnoses on the symptoms. A sonogram on the body reveals a cyst, which rules out hep C. An amoeba infection might explain everything. House orders massive doses of paromycin and chloroquine, twenty times the usual amount.
Chase informs House that Laura's heartbeat is irregular, possibly from global hypokinesis. House orders the meds stopped. Either they're wrong and her heart is unusable, or the treatment they need to give will make the heart unusable. House apologizes to Donald and says he can pull the plug. Donald refuses. He thinks House must be an amazing doctor because nobody who's that big of a jerk would be employed. Donald presses House to look for something missed. He has to save Henry.
The team looks for alternate theories. Chase notes that their amoeba theory is proved by Laura's heart rate returning to normal when they stopped the meds. Cameron wonders if it is toxins instead of an infection. House orders another tox screen and sends the team out to search Laura's environment.
Back at the hospital, the blood flow to Henry's brain begins dropping. Chase inserts a balloon to assist the flow. At Laura's home, House finds a bottle of diet pills. Cameron acquired photos of nude teenage boys at the school where Laura worked. Her school principal assumed Laura confiscated them from students. House wonders if she was having sex with the boys. What if the cyst was actual a scar from gonorrhea? House orders ceftriaxone as a treatment.
Laura tests positive for gonorrhea. Cameron starts the meds, which should clear up the heart in four to five hours. Chase alerts them that Henry has fallen into a coma. They must do the transplant now or Henry loses his brain from a lack of blood flow. House makes the call to the transplant team.
As Donald observes the procedure, Cameron prepares to tell him about the gonorrhea. Yet Donald breaks down and confesses to a one-night stand where he contracted gonorrhea. He didn't admit it earlier because he thinks he gave it to Laura, which made her sick and caused the accident.
As Henry awakes after the surgery, Chase tells him that he will have a case of gonorrhea in his system for a time, but he'll be fine in the long run.