Eleven year old Jane climbs a rock wall at a gym. Her mother, Maggie, coaches her from below. Unable to climb anymore, Jane slips down the wall and propels downward. Maggie cannot grip the rope holding her daughter because her hands have become paralyzed. Jane plunges to the floor and lands on her arm.
Foreman, Taub, Thirteen and Kutner review the case of the hand paralysis. House enters and pulls down Kutner's Christmas decorations. Thirteen explains that Maggie's mother died of breast cancer when she was young. Maggie inherited the BRCA1 mutation so she underwent a preventative double mastectomy. House tells the team to MRI the woman's chest to see if she still developed breast cancer.
After talking to Jane, House discusses with Wilson the role of lying in interpersonal relationships. House is annoyed that Maggie claims to be so forthright with her daughter. He senses that there is a lie somewhere. Wilson gives House the results of Maggie's MRI. She does not have breast cancer.
House wants Taub and Foreman to follow up with Maggie's recent multiple sex partners. They meet with Roger, who admits giving her the drug ecstasy. They take his stash for examination.
In the clinic, House examines a young woman for strep throat. He deduces that she must be a prostitute. Taub tells him that Kutner is starting Maggie on hemodialysis while Thirteen examines the ecstasy. During the treatment, Maggie loses her sight.
The team gathers in the office to confer about the case, but House has prepared a Secret Santa game for the group. Thirteen reports that the ecstasy is clean. Foreman suggests that Kearns-Sayre Syndrome fits the symptom of blindness. House wants Thirteen to go to the patient's home to find her computer. Taub wonders if the patient has Multiple Sclerosis. House orders an MRI for MS and a fluorescein angiogram of the patient's eyes.
In the doctor's lounge, Wilson asks House about the Secret Santa for the team. House intends for it to start infighting among them.
Kutner and Thirteen return to the hospital with the laptops from Maggie's apartment. The eye test is negative and there is nothing abnormal on the MRI. As the team looks on the patient's computers, Foreman suggests that perhaps her brain has a conversion disorder where her mind is tricking her body.
House asks Jane to lie to her mother because it will help diagnose her. Taub pretends to administer medicine to Maggie and tells her that Jane has to stay out of the room.
The doctors realize that House gave all of them his name in the Secret Santa game. They debate whether to even get him any presents. Meanwhile, Maggie is unable to breathe as her lymph nodes swell and cut off her airway.
In House's office, the team searches Maggie's emails for any information that might help them. House announces that she suffers from sarcoidosis. From the emails, he sees that she has had trouble walking for a while. House opens a gift that has been sitting on his desk. It is an iPhone. Thirteen thinks House gave the gift to himself, but House is pleased that he caused the team to argue.
Maggie is given a bronchoscope test on her lungs. At the end, her eyes start to bleed. She does not have sarcoidosis and her blood platelets have dropped. The team scrambles for answers. Kutner tells House he is his secret Santa and hands him a small gift.
In the clinic, House treats the young woman with strep. He asks if she performs a donkey show. She says yes and invites him to it.
Chase and Foreman perform a bone marrow biopsy on Maggie. The drill, however, cannot penetrate her bone.
Maggie is in her room after being given a full body bone scan. The team bickers about the scan. Foreman suggests that perhaps her entire skeleton is turning to stone. Kutner mentions carbonic anhydrase type II deficiency genetic disorder. House orders blood tests. If it is positive, then she will need a bone marrow transplant. Jane is the best donor choice, but Maggie forbids her daughter from doing so.
The results show that Maggie is suffering from something worse than CA-2 deficiency. House orders the team to research the cause. Jane comes into the lab and says she wants them to test her bone marrow.
House questions whether Jane is not really Maggie's daughter. Maggie confesses that Jane's biological mother was a drug addict who didn't want the baby. Jane bluntly tells Maggie that she is going to die.
House enters the Christmas party in the lobby, and grabs Wilson. House says he is impressed by Jane's ability to tell the truth.
House comes to the lab, singing. House tells the team to give Maggie an anti-psychotic drug called risperidone. House explains why as he examines the patient. Although they discounted breast cancer in the beginning, sometimes extra breast tissue is found in areas of the body where it does not belong. Risperidone causes breast tissue to swell, making it more detectable. She could have breast cancer outside of the breasts. House finds a lump at the back of Maggie's knee. He stabs a syringe into it as white liquid pours out. He tells Jane to open her mouth and he squirts the liquid in. Risperidone causes galactorrhea, which is milk production. House calls for chemo and removal of the tumor to treat Maggie.
As House exits the hospital, he walks past his team who is at the hospital party. His scheme to split them up failed.
House enters a church service in the middle of a living Nativity scene. The woman from the clinic is playing Mary. She rides in on a donkey. House exchanges knowing glances with her.