An 8-year old boy named Jasper gets a bloody nose at day care. His father Deran arrives and learns that Jasper was involved in a fight. The teacher seems concerned about the blood that has been flowing for ten minutes, but Deran remarks that this isn't Jasper first nosebleed. Deran then turns to see his daughter Lucy on the floor of the day care. She is gasping for breath.
Later, Cuddy presents House with Lucy's file and declares constrictive pericaditis, an affliction usually found in much older people. The girl is in surgery. House throws the file at his team, tells them to check for sarcoidosis, amyloidosis and hemochromatosis. He then leaves for the night.
Having stayed up all night, Foreman and Cameron inform House that all of the tests were negative. Chase went home for a full night's sleep because he figured the tests would be negative. He comes in that morning with the pathology report. They found granulomas in Lucy's pericardium, which indicates a fungal infection. House orders Cameron and Chase to biopsy a lymph node. They must do it together.
Chase and Cameron begin the biopsy. During the procedure, Deran reveals that their mother died last year of brain cancer. Jasper begins flirting with Cameron. Lucy asks for her bunny, but when Cameron tries to hand it to her, she just flails at it. Lucy says she didn't know which bunny to grab.
Cameron tells House that the girl's double vision led them to a slit lamp test, which showed that the eye's anterior chamber is swollen. This is a sign of uveitis. Chase announces that the lymph node biopsy was clean. Foreman declares that vision issues plus heart troubles most likely equal autoimmune disease. House asks if Lucy's knees are scraped up. Most 6-year olds like to play outside, but Lucy doesn't. Is that because running around hurts Lucy's joints?
Foreman informs Deran that the doctors suspect Juvenile Rheumatoid Arthritis. Fortunately, they caught it early, which gives the best chance for a good outcome. Lucy then sits up in bed. Her left eyelid and left side of her mouth droop. Foreman recognizes a stroke.
The stroke was caused by a blood clot in the middle cerebral artery. Cameron brings up polycythemia, or thick blood. House realizes that thick blood would possibly explain the stroke and the autoimmune response. A lack of oxygen would cause overproduction of red blood cells, which thickens the blood. House tells Chase and Cameron to check out the family home for possible environmental causes. Cameron snaps about being punished by forcing them to work together. House says he'll be happy to fire one of them if they can't get along.
As Chase and Cameron head out, Jasper runs up with a bouquet of flowers for Cameron. He stole the flowers from a family with a newborn. Cameron takes one flower and kisses Jasper on the cheek before sending him back. Elsewhere, Foreman drains blood from Lucy to help the flow and reduce the chances of another stroke.
Inspecting the home, Chase finds multiple letters from school about Jasper getting in fights. Searching Lucy's bedroom directly above the garage, Cameron finds a vent under the bed. She and Chase check inside and find a child's t-shirt stained with blood.
Cameron tells the team that she suspects Deran is abusing Lucy. House is upset mainly because they need to spend a day figuring out if this is abuse or a relevant symptom to Lucy's case. Foreman bluntly asks Deran if he's abusing his daughter, showing him the t-shirt. Deran angrily denies it, but Foreman gives him two choices. He can either consent to the exam or the hospital will call social services, who will force him to consent.
Cameron performs a full physical check on Lucy, including a vaginal exam. To her shock, Cameron finds cuts all over Lucy's genital area. They are almost like slices. Some are almost healed but some are fresh. However, the cuts are not deep enough to account for all of the blood on the t-shirt. There also isn't any vaginal tearing. Foreman wonders if the blood on the shirt isn't Lucy's.
Lucy's blood is tested and contained endometrial cells. Another test showed that it was definitely her blood on the shirt. Six-year old Lucy had menstrual blood and has started puberty. Cameron explains the diagnosis to a stunned Deran. Excess sex hormones can confuse a body, leading it to blossom prematurely.
The team figures that a pituitary adenoma is spiking Lucy's hormone level. House instructs them to look for a tumor in her brain. If it's not there, it's probably in the reproductive tract. They are to start from the top and work down. Cameron, arguing that it could be hormonal additives in the chicken fingers and milk Lucy lives on, is going to check for estrogen. The MRI reveals a solid tumor on Lucy's left ovary.
A worried Wilson catches up with House. He took Cuddy to a play that House gave him two tickets for. Now Cuddy has sent Wilson thank you flowers with a card saying they should do it again soon. Wilson is panicking that House was right. Men and women can't be friends and nobody goes to a play platonically. After Wilson runs off, House smiles at Cuddy and tells her he sent Wilson some flowers.
Jasper finds Cameron in the hallways and asks if Chase is her boyfriend. If he isn't, then Jasper wants to be. Cameron walks him back to his father and he grabs her rear.
Foreman and Chase perform a laproscopic biopsy on Lucy when she crashes. Foreman has to shock her back to life. The biopsy shows that the supposed tumor is actually a benign cyst. Cameron gloats that her suspicion of hormones in Lucy's environment must be the right direction.
Late that night, Chase and Cameron are grabbing some coffee when he says she must have feelings for him. He tenderly grabs her arm. Suddenly, Jasper comes running in screaming that he'll kill Chase if he touches Cameron. He bites Chase. The doctors call House to tell him what happened. House realizes that Jasper is out of control aggressive, and the cause is probably extra hormones. Whatever Lucy has, Jasper has it too.
A test shows that Jasper has 100 times the testosterone of a normal 8-year old. The team hasn't found any hormone-secreting tumors in his body. Chase raises the issues of genetics. A brain tumor killed the mother, so perhaps the kids have one too. As Foreman performs a bleed on Jasper, Lucy begins crying out that her stomach hurts. A new MRI reveals a cyst in Lucy's pancreas, two more in her kidneys and one in her lungs. They weren't present 48 hours ago.
Chase learns that the mother was perfectly healthy until she got cancer. Genetic causes are thrown out. Environmental causes have already been thrown out. Cameron insists that it has to be a pituitary adenoma, even though a scan has yet to reveal one. They should remove the pituitary gland. House says no, but Cameron argues that this is exactly how he does things. They've eliminated every other answer. Brain surgery is all that's left.
Cameron presents Deran with the options, pressing for surgery. House appears and attempts to submarine Cameron's efforts, arguing that they don't really know what's happening yet. Cameron presses about environmental causes, but the only possible option is that they both attend the same daycare. However, Deran points out that none of the other children are sick. He signs the consent form. House asks the man how he knows the other children are healthy if he's been in the hospital for the past four days.
House visits the daycare and accuses the supervisor, Janie, of dating Deran. She admits that she is, but stresses that she's never been to the home. House stares at her, noticing a red rash on her upper lip. She confesses to having a mustache wax over lunch. House calls the hospital and tells them the cause is Deran.
House returns to the hospital to confront Deran, who says Janie is so much younger than him and he has trouble keeping up. He's been using a male enhancement cream, which House points out is loaded with testosterone. Every time he hugged the kids, they received some of the testosterone Deran was excreting through his skin. If he stops using the cream, Lucy and Jasper will be fine.
That night, Wilson comes into House's office, still in angst over the flowers. Wilson wonders if this is worth exploring. He decides to march down to Cuddy's office and, without a word, kiss her. House encourages the bold move. Wilson leaves, and after a moment, bursts back into House's office, enraged that he was going to let him go through with that. He knows House sent the flowers.
House and Cuddy watch as Deran leads Lucy and Jasper out of the hospital. Cuddy laments the freakish nature of the kids' problem, wondering why it's so hard for people to find a suitable mate. House looks at her and then mentions that he has two tickets to a play.