Instead of, you know, going to the operating room to stop the unnecessary surgery that will change Alice's life forever, Chase instead runs to House and tells him to do that. Alice doesn't have necrotizing fasciitis; she has erythropoietic protoporphyria -- an allergy to light. House shrugs Chase off, saying that his infection theory is better. Chase says that the light allergy explains everything -- every time Alice got worse, it was when she was either under hot surgical lights or when he father took her outside into the sunlight. House says that doesn't explain the liver, and tells Chase to get out of his way. Chase will not move and even gives House a slight shove backward, so House punches him in the face. Well, at least he didn't tell Chase that he was a failure as a parent. House even seems shocked at his behavior, and Chase takes advantage of that to explain that the light damages the blood cells, which contain protoporphyrin, which builds up in the liver. And that explains Alice's liver damage. Meanwhile, other hospital workers calmly walk past the scene, not even stopping to think about how this is the coolest thing they've ever seen.
Alice gets a stay of limb execution just in time. Phew!
Cuddy explains Alice's illness to her parents, who are not totally pissed off at PPTH for almost removing their daughter's limbs unnecessarily after taking guardianship of her away from them. But anyway, Cuddy says that Alice has had the illness all along, but only now did the accumulation of the protoporphyrin in Alice's liver get bad enough to cause problems. The liver damage was what caused the gallstones, which means that, thanks to House, Alice is now minus one gallbladder and can look forward to digestive issues for the rest of her life. She can also look forward to a life of special lightbulbs, filters on her windows, no going out in the sunlight without basically wearing a burkha, and, worst of all, homeschooling. The parents might want to consider moving Alice to Alaska or someplace with six months of darkness so that she can sort of have a normal life. The parents' first concern, of course, is which one of them gave Alice the genes for this illness. Man, they will blame each other for just about anything, won't they? Cuddy rolls her eyes and says that they'd both have to be carriers for Alice to get it, and that when Alice wakes up, they should consider not being total jackoffs to each other. And Dad might want to consider shaving, because only House can pull off that ridiculous 5 o'clock shadow Dad's been sporting all episode.