The PI admits that he's not very good at disguises. Foreman doesn't even blink before asking House who this guy is. House says he's a "very bad" private investigator. Taub asks why he's undercover. House non-explains that he wanted to hear what they found out about the donor before hearing what the PI found out about the donor, so he'd know whether or not he needed the PI in the first place. Then ... just ask them without the PI there. Or have him there, but let Kumar and Taub speak first and him second. Whatever. Kumar says the donor came up clean with no history of infections or international travel. At this, PI giggles again. It turns out the donor went to Madrid and the Bahamas, both of which are a den of bacteria, I'm sure. The trips didn't show up on donor's credit card receipts because his girlfriend paid for them. The donor was a kept man. Kumar says the guy didn't have a girlfriend, but it turns out that she was his best friend's wife. And she gave birth to a kid who was conceived right before the donor died. Guess whose? Foreman asks if the PI found out anything medically relevant. "The kid has a tummy ache?" PI says. Oh, and the donor and his cheating girlfriend's "sex pad" was full of toxins. And with that, he hands House a receipt for $2300. House says he'll pay by check. The PI isn't stupid; he only takes cash. House admits that he had no intention of actually paying the PI so much, but the PI says his fee includes footage of the MMA bout from several different camera angles that he got from attendees' camera phones. House folds his arms and falls in love.
Later, they've watched all of PI's footage and found that the fighter's pupils were dilated before he went down. But he didn't drop his hands, which Foreman says means he was able to keep his muscle tensity. House just wants Foreman to admit that he was right. Foreman does, then continues that the fighter had a temporal lobe seizure. Kumar just wants to know if the new PI means they don't have to break into people's homes anymore. Not bloody likely. As House points out, the Cottages are free. The PI costs big bucks. With that, House orders Foreman to biopsy Apple's brain. Foreman refuses, since the procedure could turn Apple into a vegetable. At least she'll stay in the same food group. House just shrugs and suggests biopsying the brain of the patient who is "almost finished" with his life as the camera pans over to Frank's side of the room. Hadley is furious and accuses House of ageism because she's a moron. House has to explain that this has nothing to do with how old Frank is and everything to do with how little he has to lose at this point if the biopsy goes wrong. He'll die if they don't do anything. "Get the widow to say yes," House says, leaving. Word of advice to the Cottages: don't address the wife as "the widow." She probably won't like that, since her husband is still alive and stuff.