Fifteen year-old model Alexandra Simms waits impatiently backstage at a fashion show. Her manager father, Martin, hands her a pill to steady her nerves. She washes it down with a glass of champagne. On the runway, Alex starts seeing double and stumbles. When another model asks her if she is fine, Alex punches the girl. Chaos ensues and Alex collapses in the mess.
House limps through the hospital, struggling more than usual with his leg. Wilson thinks the increased pain could actually be good sign that his nerves are regenerating. House brushes off his optimism. Cuddy approaches with a new patient file. A teen model has sudden aggressive behavior and cataplexy.
House drops into Alex's room. The cataplexy checks out with Alex's story, and House asks about sweats and other recent ailments. She claims to have been nauseous lately. Cameron waits in the hallway to grill House about his newfound interaction with patients. He orders her to do the tests and tox screen.
The tox screen reveals Valium and heroin in Alex's urine. Cameron notes that a positive test doesn't mean Alex is an addict. Chase wonders whether this is related to the fact that Alex has yet to menstruate. They also consider bulimia and the patient's newly developed breasts. During the brainstorming, House's leg buckles and he nearly falls. Even with addiction, Alex's symptoms could be neurological, which points to juvenile MS or Parkinson's. House orders a detox program at super speed. He wants them to put Alex in a coma and pump her full of naltrexone, which cuts the detoxification procedure from four weeks to one night.
Foreman explains the procedure to Martin, who agrees despite the risks. Chase and Foreman prepare to put an incredibly nervous Alex into an induced coma. Alex's heart rate dips below 30 before flat lining. Nurses rush in and go to work on the girl. Martin finds House and demands that he pull Alex out of the coma. House explains that this option is even worse. The must see the procedure through.
Alex regains consciousness from her coma. She tells Chase that she feels fine. Alex tearfully apologizes to her father for using drugs. Chase begins to hook up a potassium IV, and Alex repeats what she just said. Back in the office, Foreman reports anterograde amnesia and short term memory loss which is evidence of a hypoxic brain injury. Foreman blames House for pushing the rapid detox. House points out that Alex would have to flatline for longer than she did for hypoxia to kick in.
House suggests that Alex suffers from post-traumatic stress disorder. She looks too good to be a heroin addict. With Daddy constantly by her side, House thinks Martin is either a very good father or a very bad one. He suspects sexual abuse, and orders an MRI and LP. If Alex's brain comes back normal, House will have his proof. Out in the hallway, Foreman accuses House of letting his increasing leg pain influence his judgment. He's trying to rush through this case. House turns and loudly asks Martin if he's molesting his own daughter.
Alex goes through the MRI. Yet she has an involuntary shoulder twitch which will mar the MRI. Cameron thinks they should skip right to the LP. Slipping into a men's room for privacy, House continues pressing Martin. He denies abusing his daughter. House asks if Martin loves Alex enough to admit what he did, since psychological conditions can manifest into physical problems. Martin confesses that it happened once.
House finds Cameron and Chase in the lab and happily reports that he was right. It is now time to move Alex onto a psych referral. Chase shows House the results of the LP, which show elevated proteins in Alex's CSF. It wasn't hypoxia and it wasn't even the sexual abuse.
Cameron presses House to report Martin to child services, but House wants to finish the case first. Foreman starts running down the list of problems that would cause elevated proteins in the CSF: viral encephalitis, CNSV, Creutzfeldt-Jakob disease. House thinks they need to skip straight to a brain biopsy. The team is hesitant because this is too rash, but House is convinced that it is the only thing they have time for. They must perform a burr hole biopsy to remove a small section of brain tissue.
Wilson tells House that he heard about Alex flat lining. He wonders if the leg is affecting his judgment. House quietly confesses that he needs Wilson's help. Meanwhile, Cameron goes to Cuddy about House not reporting Martin.
The biopsy gets underway while Wilson performs an MRI on House. Cuddy barges in, demanding to know about Martin. If House doesn't turn Martin in, he's fired. Wilson gives House the results that his MRI looks the same as it did two years ago. It might be psychological pain manifesting itself as physical pain, caused by House's misery over driving Stacy away. House refuses to accept this.
The biopsy on Alex shows that she does not have a white matter disease. That leaves grey matter, which uncorks a range of possibilities which can't be tested. House asks if what they are seeing could merely be smoke signals from a tumor. If Alex had cancer anywhere in her body, she could have paraneoplastic syndrome which would cause antibodies to attack her brain. Foreman counters that this is rare in a 15 year old, but House points out this is no ordinary teen. What's more, it explains everything.
House squeezes an IV line on Alex and she immediately starts twitching. When he releases it, she stops. House explains that IVIG vacuums her blood and neutralizes the stuff that makes her twitch. Although Martin and Alex are excited by the development, House explains that merely proves that she has cancer.
That night, House asks Cuddy for a favor. He wants a shot of morphine in his spine. She refuses and tells him to take a Vicodin because morphine is too extreme. Desperate, House pulls down his pants and exposes his scarred and mangled leg. His skin has been indented by the lack of muscle. Cuddy agrees to the shot.
Alex receives an MRI, a mammogram and a bone marrow biopsy among other tests. Wilson can't find any cancer but House insists that he is wrong because nothing else could explain the IVIG. Wilson is adamant that she does not have cancer. House retreats to his team and asks for a differential diagnosis. Chase wonders if the protein level was an anomaly. It might really be the post-traumatic stress disorder from Martin's molestation. Alex saw House fiddle with the IV line so it could all be in her subconscious. House tells Chase to change Alex's IV, but don't inform her that he is replacing it with saline. They will see if the twitching returns.
As the doctors wait, a social worker from Child Services interviews Alex. The social worker exits and informs the doctors that no charges will be pressed because Martin denies telling House. Alex says that nothing happened. Cameron goes into the room and tries to convince Alex to tell the truth. Alex doesn't go back on her statement. When Cameron presses, Alex admits that she seduced Martin and got him drunk because she wanted to have sex with him. She also slept with her photographer, her financial manager and her tutor. It's the only way to get what she wants. The twitching returns.
House asks Cameron, who performed Alex's vaginal examination, if she had pubic hair. Cameron says that there wasn't much. House wonders about Alex's real age and he schedules another MRI. Cameron complains that an earlier MRI showed no tumor but only undersized ovaries. The new screen finally shows what House has been looking for. It looks like a tumor, but it isn't.
Martin asks House if they found cancer. He says there is a tumor on Alex's left internal testicle. House explains that Alex has male pseudohermaphroditism. All humans start out as girls but then get differentiated by genes. With men, the ovaries develop into testes and drop. But in about 1 in 150,000 pregnancies, something else happens. Alex is completely immune to testosterone. She is full of pure estrogen, which explains the clear skin and perfect breasts. When they remove her testicles, she will be fine. Alex does not handle this news well.
House approaches Cuddy for another shot of morphine. She thinks it's curious that the pain returned after House solved Alex's case. He says he only wants a shot, not a psych session. Cuddy calmly tells him that when she administered the shot, it was only a placebo full of saline. House realizes his pain is indeed in his mind.