Kutner and Cole are in the audience of a magic show in a night club in Atlantic City. Finn, the magician on stage, is replicating Houdini's famous water chamber trick. He calls Cole up to the stage. Wrapped in chains, Finn is dropped in the tank but loses consciousness as soon as he enters the water.
Back at the hospital lecture hall, a bored House announces a contest for the Fellows. The winner will be spared from getting fired and will get to nominate two competitors. House will choose one from that pair to get the axe. Kutner suggests taking the case of the magician. He wants to run tests to find out why Finn's heart stopped in the water. House is sure the magician was faking. If Kutner is wrong, then he is fired. House declares that the contest objective is to retrieve a pair of Cuddy's underwear and bring it to the group. The Fellows debate taking the challenge. They will.
Thirteen helps Kutner examine the patient. Finn has her to pick a card from a deck and then asks Kutner for his wallet. He sets the wallet on fire. The card she picked is inside of it.
Taub and Amber conspire to obtain Cuddy's underwear. Amber tries to spill coffee on Cuddy, but that doesn't work. Then Amber smokes a cigarette to set off the fire alarm. Yet Cuddy stands with Taub away from the sprinklers and fully dry.
Kutner tells Foreman that the tests show there was no cause for the heart failure. Foreman suggests running a lung MRI. Finn suffers from internal bleeding. He has had three units of AB positive blood transfusions, so Thirteen considers that he has an intestinal infarct. She drops her files.
Taub enters the MRI unit with Cuddy's black panties. House, however, says that Cuddy is wearing a red bra. He deduces that Cuddy would be wearing red panties to match her bra. House asks Amber to lift her skirt. She refuses. House knows that Taub and Amber cut a deal. The black ones are Amber's.
While Finn is being operated on, House steps in and sticks his hand in Finn's gut. He pulls out a key. After Finn wakes, House informs him that the MRI magnet ripped it through his intestines. House tries to debunk him. The playing card that House chooses from Finn's deck is stuck to the glass wall. Finn refuses to tell House how he performs the trick. Suddenly, the magician starts to bleed profusely out of his nose. House realizes something is still wrong.
House gathers the Fellows in his office. He declares the underwear challenge is now off. Finn's cardiac arrest is actually a symptom of something more serious. Shockingly, Cole produces the panties. Amber proves that they're not hers, and then she suggests that Finn has Polyarteritis nodosa. Taub throws out the possibility that the nose bleed was caused by cocaine. House tells Taub and Kutner to go to the patient's home. He orders Amber and Cole to do a biopsy of Finn's heart. House tells Thirteen to come to his office. He thinks she is hiding a medical condition from him. She denies it.
Kutner and Taub find old arcade games, rabbits and marijuana in Finn's home. Taub theorizes that the rabbits could have given Finn pericarditis from a tick.
House demands to know how Finn did the card trick earlier. Finn performs a slight of hand with House's vicodin pills. They continue a discussion about knowledge of truth versus the magic of the unknown. House says it is better to know how things work and put all the pieces together. He diagnoses Finn with tularemia from his rabbits.
In the hallway, House drops his vicodin bottle so that Cuddy will bend down. He is amazed when he sees no panty line. He asks Cole to tell him how he was able to get her pants off. The Fellows interrupt because Finn now has bleeding around his heart. It could be cancer. House notices that Thirteen's hand is shaking. He tells them to find where the cancer is located.
As Cole gives Finn the MRI, Amber tries to influence his choice on who should be kicked out. Finn predicts that he will be dead by the next day. The doctors notice that Finn is bleeding inside all over.
Kutner considers a tainted blood transfusion. Foreman says that the low immunoglobulin levels and the other symptoms indicate amyloidosis. The Fellows' pagers go off at the same time. Finn has had a grand mal seizure. As Kutner and Cole attend to the patient, Kutner reminds Cole that he is his friend and should not be nominated for elimination.
While playing foosball, Wilson and House discuss how Cole could have gotten Cuddy's underwear. Kutner and Thirteen enter with the news that Finn has kidney failure. House believes that this proves the diagnosis of amyloidosis, and not a bad blood transfusion as Kutner suggested. House believes that Finn needs a bone marrow transplant. Wilson says that the patient needs to be irradiated first. House wants a subcutaneous fat biopsy taken and gives the Fellows two hours to check the blood theory.
Taub offers Cole $5,000 to not be chosen. In the hospital blood bank, House checks in on Foreman, Thirteen and Kutner's progress tracking the blood. Cole finds that the biopsy is negative. House wants them to next test Finn's organs. Yet Foreman no longer thinks it was amyloidosis. House wants to put the blood in his own body to see if it is tainted because he is the same blood type.
As Thirteen gives House the blood transfusion, he tells her that he saw a picture of her mother in her wallet. He explains that he Googled the obituary and knows her mother died from Parkinson's disease at young age. Thirteen admits that she may have inherited Huntington's chorea disease. House says that he has been switching her decaf coffee with caffeinated to see her reactions. Yet she refuses to be tested for the disease because not knowing her fate encourages her to live life fuller.
House falls sick from the blood transfusion and passes out. Thirteen tests his organs and admits that she spiked his tea. She leaves a bottle of water in the room. Wilson stops by House's office to see how he is. Wilson is type O, according to House. Wilson worries how House knows that. Did he test his blood? They realize that they gave the magician the wrong blood type. Finn tells House he is type-A blood. He is not AB, but his body is making an extra antibody of type B. That explains the symptoms after the transfusion. House says all the other symptoms point to Lupus.
House enters the lecture room with the underwear of Cuddy on a pillow. He asks Cole to nominate two candidates. Cole chooses Amber, the cutthroat bitch, and surprisingly, Kutner. House realizes that Cole made a deal with Cuddy to choose who she wanted out. In Cuddy's mind, Kutner's history of accidents means he is a liability to the hospital. House wanted someone to subvert Cuddy instead of dealing with her. He fires Cole.
Thirteen enters House's office with an envelope that contains her genetic test results for Huntington's. House had them performed from her DNA on the water bottle. Thirteen says that the not knowing is what gives her hope and that this is all she has to go on. House tosses out the unopened envelope into the trash.