The case is so important that Cuddy joins the team for the differential diagnosis. Melinda's immunocompromise is only temporarily, the result of that heart transplant she had six months ago. Well, I am shocked that the Evil Transplant Committee Overlords would deign to let the girl have a heart after all those other people they've rejected. It makes more sense that Cuddy's there, though: she wants to make sure that the heart they gave out actually lasts. Plus, if Melinda dies, they can put "teenagers with allergies" on their long Recipient Reject list. House throws it over to her with the obligatory comment about her panties that Cuddy shrugs off like the cool lady she is. I really missed those two and their witty, if completely inappropriate for the workplace, repartee. She fills the group in that the patient has been at PPTH four days, undergoing every test under the sun, but that they've found nothing to trigger her allergic reaction. Chase suggests that Melinda might have an exercise allergy, which I refuse to believe actually exists. Being allergic to exercise is like being allergic to working for a living or allergic to homework. Nevertheless, I'm sure we'll be seeing it in a future episode. House likes this idea, simply because it allows him to describe their minor-child patient as a "nubile teenage nymphet," but Cuddy nixes it, saying that the Mother was in the room seconds after the attack occurred (although not so quickly that the girl wasn't about to pass out from lack of oxygen) and there was no funny business going on or anyone hastily pulling their pants up when she came in. House and the Cottages come up with the theory that either Dan brought in the allergen or the girl snuck out her room, or that the parents just didn't do a good enough job keeping the room sterile. Every option means that someone lied, since Dan, Melinda, and the parents have all denied these allegations so far. "These are your big ideas?" Cuddy sneers. "Somebody's lying?" Someone needs to check her out, since she's obviously having an amnesic attack wherein she's forgotten the last two seasons. House orders the Cottages to re-check all the people and the bedroom for allergens.
Parents, daughter, and boyfriend are assembled in the hospital room. Foreman asks them if they brought any new soap into the house, or if Melinda might have snuck out of it, which I'm sure she'll be happy to admit in front of her parents. Both charges are denied, Melinda adding her own commentary about how her parents keep her trapped in the house like a prisoner and she demands that Foreman tell her parents that she's better and can be let wild and free again, a request that might have a little more weight behind it if the requestor wasn't sitting in a hospital bed after almost dying a few days ago. Stupid. Foreman says that if they can find out what she's allergic to, then her chances of being freed from the confines of her bedroom are good, at which point Melinda snots an "I told you so" to her mother, who snots a "can I speak to your outside, please" to Foreman.