House spends the night in his office, thinking. Cuddy stops by to tell him that she's signing off on his 120 hours after all. House thinks she's letting him skip the rounds because she's uncomfortable around him. Cuddy denies this, even after House says being around her makes him "feel funny." He appears to be kidding, but not really. "I was kinda getting into the whole hot-for-teacher thing," he says. Really? Didn't they have, like, three seconds of rounds together? Cuddy asks House if he's "sure" he's okay. House says it was a "false alarm" but doesn't go into the details. "What about us?" he asks. Where is this coming from? They've had minimal interaction all season and no sexual tension in the few scenes they have had together, and now all of the sudden, this? Huh. Cuddy says the way things are between them now is the same as ever; "you press my buttons, I press yours." And that gives House his epiphany moment. He sets off for Donny's room, taking an extra second to invade Cuddy's personal space and say "you do make me feel funny."
House enters Donny's room and informs him that he has a "self destruct button" in his brain. Actually, it's a berry aneurysm, which can apparently be inherited. It grew throughout Donny's (and his father's and his father's and his father's) life and pressed against the nerves that control things like tooth pain and heart rate until around the age of 40, when it got so big that the signal to the heart stopped entirely. Although that doesn't explain why Donny's heart is beating just fine right now. Did the aneurysm somehow shrink a little bit when he fake died? And how did it grow so large in just one day that Donny had that intense tooth pain but it took 40 years to stop his heart? And surely doctors would have been able to see an aneurysm was the cause of death for his father -- they're pretty easy to see in an autopsy. Not to mention the CT scan Donny must have had done on his head when he was admitted with that concussion should have seen something, right? Anyway, Donny has some trust issues with House since the last time they spoke House sent him home with a fake diagnosis and then Donny sort of died. House says he's willing to prove he's telling the truth by signing both Donny and his son up for brain surgery. Donny seems relieved to hear that his son will be okay, but when House rather kindly offers to let Michael come in for a visit ("visiting hours don't apply to my patients"), Donny hedges. House takes this to mean that Donny won't be calling Michael at all -- now that he doesn't have the excuse of sparing Michael from the pain of losing a father, the fact is that Donny likes his selfish life and doesn't want to be burdened with the responsibility of a son.