There are cysts all over Lucy's internal organs. The hormones, Foreman explains, are causing the cysts. If she gets one in the wrong place, she'll be dead. Cameron and Chase finish looking through the mom's medical files and find nothing of import. Cameron concludes that they've ruled out environmental and genetic causes, so it must be a pituitary tumor. One of those special ones that siblings coincidentally get at the same time but no one can see on the scans. House thinks it must be environmental, but the Cottages protest that Lucy is out of her environment and getting worse and they haven't found anything in her environment after a night of testing. Cameron decides to take matters into her own hands, just like Chase and Foreman did when they decided to go home and let everyone else do the work. This time, House does not congratulate her gumption, but instead tells her not to. He points out that they have no evidence that it's a brain tumor, and considering that the source is a guy who will do just about anything to his patients with evidence like "he dove into water that was cold," that's pretty big. But Cameron won't be moved unless it's towards Deran with a consent form.
House finds Cameron telling Deran to sign a consent form allowing them to remove Lucy's pituitary, the "most likely cause" of her hormone problems. House goes the full-disclosure route and says that "most likely" means that they don't know if a pituitary tumor is the problem and may very well take it out for no good reason. Cameron says that they've ruled out every other option, and House interrupts her/ignores her and asks Deran if he has a girlfriend or someone who's in contact with his children. "No one visits," Deran says, probably wondering why everyone in this hospital keeps bullying him into signing these horrible consent forms. Deran does say that while Lucy and Jasper go to different schools, they attend the same day care center. None of the other kids there are sick, though. "Yet," says House.
Cameron thinks that Lucy will die if they wait for the other kids to show symptoms. House thinks that without a pituitary gland, Lucy will be on hormone replacement therapy for the rest of her life. Cameron says that HRT is "extremely effective" and Lucy will lead a "relatively normal life." Yeah, when she's not getting the cancer that HRT has been linked to and that she's genetically predisposed towards. In other words, it's not something you want to do for the rest of your life unless you absolutely have to. Cameron thinks Lucy does absolutely have to, but House thinks she doesn't. It's really unprofessional of them to argue about it in front of the patient's family. When House seems to be getting the winning edge in the argument, Cameron is forced to pull out her trump card: "My husband died of thyroid cancer that metastasized to his brain." Deran looks at her like, "Why are you telling me this?" Cameron: "I've been there. I know how terrifying this can be." Oh, do you really, Cameron? Did you have a dying daughter to deal with after your husband died? No. House is appalled: "You did not just play the dead husband card!" Of course she did! It's all she has and the basis of all her emotional responses. House fires right back with "My wife died because she signed a consent form that I didn't want her to sign. Died," he says, overcome with fake grief. I laugh and clap my hands with glee. No, really, I do. At this point, Deran just wants these horrible people to leave him alone, so he signs the consent form. Cameron refrains from dancing in victory. House doesn't fire her and rip the form into tiny pieces. He does, however, ask Deran how he knew that none of the other day care kids were sick. "I would have heard," Deran says, looking rather shifty.