Preppy, uniformed teens perform at their school holiday show. Before the chorus takes the stage, the pretty girls of the group convince nerdy and chubby Natalie to change up the words of the song in order to make fun of a teacher. Natalie is reluctant, but eager to fit in. She starts singing and realizes that the entire chorus just played a joke on her. The music stops. Natalie suddenly starts vomiting and drops to her knees.
Cuddy briefs Kutner, Thirteen, Taub and House on the case. Foreman is taking vacation days so he can finish his FDA reports before the end of the year. House writes "liver" and "brain" on the whiteboard. Kutner considers Wilson's disease but Thirteen says that the patient's ceruloplasmin is normal. Taub notices something in the pile of mail at the end of House's desk -- a wrapped present with a note. He goes to read it, but House grabs the present and drops it in the trash. Taub rescues the gift and unwraps it. It is an antique surgical manual. House drops it in the trash again. Thirteen wonders if the kids slipped something to Natalie.
Chase and Kutner question the other children from the chorus. No one will talk. Chase tells them that their friend's liver is failing and she could die unless they confess what they gave her. One girl admits to giving Natalie some "shrooms" from Simon's locker. She points to Simon, a tall, good-looking boy.
Thirteen sits on an exam table as Foreman conducts a neurological test on her. She asks him where the other trial patient went and he says the woman dropped out. Thirteen is doing well. She leaves her clipboard for him. On it is a gift certificate. She has written, "Thanks for helping me out. XO." Foreman smiles.
At the high school, Taub and Kutner watch a maintenance man open up Simon's locker. Kutner grabs a bag of mushrooms from it. Taub wonders aloud why House would throw out a book worth hundreds of dollars. The guard opens up Natalie 's locker. Inside is a huge bottle of acetaminophen.
Cuddy confronts Natalie. She denies trying to kill herself and asks Cuddy if she has any kids. Cuddy's not sure where this is going. Natalie calls herself a loser. Kids make fun of her and call her a pig. Cuddy talks to Natalie 's parents. Acetylcysteine could save her liver.
Taub and Kutner tell Wilson about the book. Wilson asks if it was wrapped in green wrapping paper. He then tells them the sad tale of Irene Adler. House saved her with a last minute Wegener's diagnosis. He calls Irene the "one who got away." Wilson is making fun of them. He says he was the one who gave the book to House last Christmas.
Natalie coughs up pink, frothy foam. As House and the team diagnose, Taub tells House that they all know what's going on. Cuddy gave him that present. Taub thinks she loves House and he should just tell her too. Kutner and Thirteen try not to laugh. House has deduced that Taub talked to Wilson. Back to the case, House states that the patient volunteers at a soup kitchen in Trenton. Thirteen and Kutner can search the house and school. Taub will take anal swabbing of the homeless men.
House barrages Wilson's ice cream in the cafeteria. Wilson urges him to try harder to be kind. House takes this as a dare and he grabs Wilson's replacement ice cream.
Thirteen goes to see the Huntington's patient at a nursing home. The woman says Foreman told her to "get over" her nausea side effects.
Taub discovers that Natalie has gotten tuberculosis from a man at the soup kitchen. House instructs him to start her on the standard regimen. House takes a file and heads towards one of the exam rooms. He is oddly open and friendly to the young woman complaining of a headache. House calls it Beccaria's sign, a symptom of pregnancy. She didn't know that she was pregnant and claims to be a virgin in front of her celibate fiance. House suggests maybe she cheated with another man. They demand a paternity test.
Natalie suffers a seizure. Her ALT is 20 times normal, with her transaminases and PT's way up. She's going to lose her liver. Kutner suggests that the mushrooms may have triggered a severe mold allergy. House considers a fungal infection. Cuddy responds to House's chiding of her interest in Natalie. "You're confusing being maternal with being human," she says.
Thirteen tells Foreman to apologize to the Huntington's patient so that she will return. Foreman says no, and Thirteen accuses him of acting like House.
Natalie is in a better mood after Simon brings her homework to the hospital. Kutner finds Simon in the lobby, believing he is causing more trouble. Taub pulls Kutner aside, assuming that Kutner was bullied in school and is overreacting to Simon. Kutner says he was not bullied. Simon explains that he and Natalie used to be friends. He would still be her friend if the other kids wouldn't make fun of him. He used to get her a few bottles of vodka each week with his fake ID, but then she secured her own ID and didn't need his help.
Natalie denies her drinking to Cuddy, who informs her that they can't get a liver transplant until they know why her liver's failing. Alcohol abuse would explain it. The seizures could caused by withdrawal. Natalie confesses that she merely wanted an excuse to talk to Simon. Cuddy tells the parents that the treatment for withdrawal is high doses of benzodiazapenes.
House's next clinic patient is having asthma trouble. He asks if she is using her inhaler and to show him how it works. She takes her oral inhaler out of her purse and then sprays it twice on each side of her neck, like perfume. Cuddy interrupts to tell House that Natalie's parents are saying no to the benzos. House assesses Cuddy because he has no idea why she cares so much. He says Kutner should start her on the benzos for seizures anyway, because they don't need parental approval.
Foreman discusses with his drug trial partner about the patient who dropped out. She tells him not to see the patients as people, but as numbers. Science is not about human relationships -- it's about results.
Natalie's heart suddenly slows. Taub grabs a syringe of atropine from a crash cart.
House is confused by the lab report for the virgin. He reports to her and her celibate fiance that she didn't cheat. She is has parthenogenesis. A spontaneous calcium spike could prep the egg for fertilization without sperm. The couple is astonished.
Cuddy informs the team that Natalie's liver continues to fail and she has bradycardia. Atropine isn't keeping the heart rate up, so she will be put on a pacemaker. Alcohol withdrawal would cause the heart to race. Kutner adds that nothing is structurally wrong with the heart. Natalie's EKG, echo, and electrolyte panels are all normal. Cuddy diagnoses multiple endocrine syndrome. Thirteen suggests hypothalamic brain tumor. House says it could be in the blood since it is hitting all her organs. He asks about her alk phos, and the file says it is 300. House takes the file and exits. Cuddy follows.
They bring the file to Wilson, hoping it's not leukemia. Cuddy is insistent that high alk phos could also be from liver failure. Wilson emphatically says to start the girl on chemo. House thinks for a moment and decides they should perform a bone marrow biopsy to confirm. Cuddy doesn't understand why House doesn't want to treat Natalie. Wilson explains that even if it is leukemia, her heart and liver are too far-gone. There's no reason to put a dying girl through a painful treatment if it cannot save her. House is being kind. Cuddy knows he's right. She will arrange the biopsy.
Foreman calls on his ex-patient to asks if she will consider another trial with lower dosage.
Cuddy starts to second guess their decision with Natalie. Maybe they shouldn't have overlooked autoimmunes. If it isn't hepatic fibrosis, it could still be microangiopathic vasculitis. Cuddy doesn't want to give up. She sits at the chair across from House, but has to move some mail off the chair. He notices that a wrapped gift sits in the mail she just moved. House checks the card. He grabs the gift and walks down the hall towards Wilson's office. Cuddy follows. It is from the pregnant patient. He explains how he saved her marriage by showing that her pregnancy was a result of parthenogenesis. The paternity test proved that she was impregnated by another man, so he lied about the diagnosis. House tosses the gift towards Wilson and heads back towards his office with Cuddy in tow. She can't believe he faked a scientific miracle just to win a bet with Wilson. House claims it was more of an argument than a bet. Cuddy says he is confusing "nice" and "evil" by letting this woman deceive her husband. Suddenly, Cuddy stops her argument with a terrible realization. Natalie doesn't have leukemia. It's eclampsia. Natalie was pregnant.
Cuddy explains to Natalie and her parents that eclampsia can cause liver failure, pulmonary edema and seizures as well as being associated with cardiomyopathy. Natalie admits that she hid her pregnancy and her sexual relationship with Simon. The parents are stunned. She was going to give the baby away but went into labor at the soup kitchen. Natalie gave birth in an empty house down the street and left the newborn for dead.
Cuddy goes to the abandoned row house with a flashlight. A junkie squatter tells her to get out. She asks if he found the body of a baby. Another squatter is holding a tiny, swaddled mass. Cuddy convinces the woman to give her the sick baby. Cuddy brings it to Natalie. Simon walks into the room.
The hospital's holiday party is underway. Kutner exits, reporting to Taub, Cameron and Chase that Natalie was turned down for a transplant. She has a couple days at most.
Kutner approaches an apartment and knocks on the front door. He apologizes to the man who answers for bullying him in high school.
As Cuddy watches over the baby, she tells House that both sets of grandparents are putting the girl up for adoption. She is going to take the baby. House watches her for moment. She can only stare at the child. House wishes her a Merry Christmas and leaves.
Thirteen finds Foreman alone. His Christmas gift to her is getting the other patient back. Thirteen says she was wrong -- he is not like House. Foreman replies that it was really his Christmas gift to himself. They stand there for a moment in silence. Thirteen moves closer to him. And then they kiss.