Chase gives Cameron some Ativan for her meth hangover. Awww, he's like the guy who makes you breakfast in the morning, except that he's a total slimeball. Chase doesn't think they should have sex again. Cameron doesn't think Chase should presume that she'd want to. Chase explains that when two people have sex and it's a fun time, they usually do it again. "And that's when things get complicated," Chase adds, as if the fact that he had sex with her while she was high on meth and probably ecstasy and all their co-workers know about it didn't already complicate things. As a consolation prize, Chase tells Cameron that she "didn't suck" in bed. I guess Cameron's not a downtown girl.
The rat problem solved, Wilson tells House that he'll have to figure out another way to insinuate himself into Stacy's life. Wilson's suggestion is to hit another patient, but House turns that down, saying that it would be repeating himself and therefore "formulaic." And yet...House exposits that Steve has a lung infection from Stacy's cigarette smoke and will need two weeks of antibiotics and a cigarette smoke-free environment. Wilson is appalled that House brought a sick rat into a hospital full of people with compromised immune systems. House says that this particular rat infection doesn't spread to people. Wilson points out that it did during the black plague, and that rats are known to carry all kinds of other diseases and parasites that could spread to humans. House makes his "brilliant idea" face, and asks Wilson whether he noticed that Kalvin's dad was sweating. Wilson doesn't answer, but House tells him to cancel Kalvin's biopsy, since it will surely kill him.
House taps on the weird glass encasement Kalvin's dad is currently sitting in in the middle of the hallway, and orders him to come to Kalvin's room with him. Dad is reluctant until House says that Kalvin needs to talk to him. They get into the room, and House tells Kalvin that his dad wanted to talk to him. Dad senses a trap and tries to leave the room, but it's too late. House asks Dad if they used to hunt foxes back in Montana. "It's Montana," Dad says. It's not like the higher echelons of the British societal hierarchy or something, where fox-hunting would be standard, is it? But it's enough for House, who tells Kalvin that he doesn't have cancer after all: he has echinococcosis, which causes parasitic cysts they confused for cancerous tumors. Echinococcosis is transferred from foxes to people and can remain dormant for years. Kalvin says he's been tested for parasites and was negative. House says that the cysts isolate the parasite from the rest of the body, and thereby cause it not to show up in any tests, just like every other parasite on this show. I really don't know why they do tests at all. Dad tries to leave the room, but House stops him, saying he's got echinococcosis too, but in his liver. It presents just like cirrhosis except for an additional fever, which would explain Dad's frequent sweating. Testing for the parasite in Kalvin will kill him, but they can test it in Dad and his diagnosis would be enough to confirm Kalvin's. So Dad can either take a simple, painless blood test that will save his son's life (why can't Kalvin take this simple, painless blood test? I'm so confused), or refuse to do it and condemn his son to death. House thinks it's only fair that Dad tell his son his decision to his face. That's actually no problem for Dad, who strolls up and tells his son that he never seemed sorry for killing his mom and himself by not wearing a condom that one time when he was a freaking teenager. Kalvin says that he's living his life the way he wants and won't apologize for anything. Dad refuses to have the blood test.