Chase finds one of photographer Kalvin's artsy photos that used some pre-WWII broken light bulbs as props. Sadly, we don't get to see this photo, which must have had all kind of crazy stuff happening in it. As Chase explains to House back at PPTH, old bulbs used to contain beryllium, the dust of which causes berylliosis, an inflammation of the lungs. Chase's possibly-dead dad wrote a paper about it, which is how Chase knows all this. House is relieved that Chase isn't actually smarter than he is after all, and orders Cameron to get a biopsy of Kalvin's lung tissue to test Chase's theory. Chase gallantly offers to do it instead, but House says he'd rather not expose all of his employees to AIDS if he doesn't have to.

Cameron does the biopsy, wearing glasses, gloves, and a smock this time, although not a face shield, which is what I would have come in with. Covered by a welder's mask, if it were available. And a latex bodysuit. I don't play around. Kalvin says he's very sorry about accidentally exposing Cameron to AIDS, but Cameron just wants to concentrate on the biopsy. Kalvin tells her that if she wanted a sample of his fun pills to test, he could have just asked her. They're in his bag over by the chair right now. Cameron is absolutely outraged that Kalvin would bring drugs into the hospital like that, as if he were wheeling himself up to the pediatric ward and selling them off during his free time or something, but Kalvin thinks Cameron is really mad about the AIDS exposure, and says that this understanding nice act she's doing about it is both useless and boring. How is it that Kalvin knows how useless and boring Cameron is, and yet the writers insist on giving her storylines? Kalvin says he was wicked pissed when he got HIV after one stupid night, so he's sure Cameron's feeling some of that, too, especially since she didn't even get to have sex for her exposure. "This wasn't your fault," Cameron says. Huh. It appears that those prophylaxis pills have a side effect of making people much cooler about things.

Stacy finds House, apparently breaking into her house, in her attic. She's shocked -- SHOCKED I tell you! -- that House would do such a thing, even though just last season she anticipated it enough to leave cookies. House explains that he had to get rid of all that poison cheese he laid out for the rat -- which, by the way, he has named Steve McQueen. Steve McQueen spins in his grave at the thought of being named after a ball-less rodent. Or at least he will, once he stops spinning from having a freaking Sheryl Crow song named after him. House needs to keep Steve alive to find out what's making his head tilt: it could be something environmental that will also effect Stacy and Mark, in which case, House will be sure to send Mark up to the attic and lock him in there until he dies and we will all find House's unique approach to romantic competition charmingly refreshing. House waves a sample of rat piss he's collected for testing under Stacy's nose just to be extra-super-flirty, and then gives Stacy some new drugs to put in Steve's cheese. If Steve has an infection, he'll be cured. If he isn't cured, they'll know he's got a tumor. Stacy asks if Steve will be having rat chemo, but House says that Steve McQueen without hair is just not cool. "It's a blessing he died young," he says. Except that Steve McQueen was fifty when he died, putting him more at the Humphrey Bogart end of the Tragic Young Movie Star Death spectrum than the James Dean end. Stacy and House exchange warm, flirty smiles until Stacy's phone rings. It's Mark, and he's coming home soon. House takes off, making sure to lift Stacy's toilet seat up as he goes, either to indicate to Mark that he was there or to piss Stacy off at Mark's inability to be polite about putting the seat down. Or both. House is crafty like that.