His diagnosis just got another layer. A physician telling a patient she's going to die really shouldn't be happy, but a patient being told she's going to die really shouldn't be the same as she was before. Like half the people in this episode, Addie's depressed.

She also chose a strange way to commit suicide, by making kitchen cleanser into a pill, which burned a hole in her intestine, created a bridge between an intestinal vein and an artery, and allowed bacteria to flood through her body. "Surgery to fix the bridge will take two hours. Psychotherapy'll take a little longer," House tells her.

Even though he's solved the puzzle, he goes further, wanting to know why she did it. "I don't know. I've just never been happy," she answers. Depression just might be the unsolvable mystery, at least if he refuses to consider it as a medical mystery instead of an emotional mystery.

Part of the beauty of the character of House is that we're never given a simple answer for why he is the way he is. His leg hurts, his lover betrayed him, his father abused him, but none of that is offered up as a simple equation to explain him away. Like House, Addie can't offer an explanation for unhappiness, though unlike House, she uses excess kitchen cleanser instead of excess Vicodin to deal with it.

He breaks his word that he won't tell her parents if she promises not to attempt suicide again, and makes them think about looking into anti-depressants as well as therapy ... because while the mystery is solved, the patient's life is still at risk. And maybe, just maybe, he can see himself in her.

Cuddy gives Foreman one last thought as they watch Addie's surgery. He thinks she's trying to tell him that House's success rate is all that matters, but she says: "I'm telling you there are worse things to turn into." Foreman remains unconvinced, though: "It's not worth it." I get the feeling House might agree.

House takes full advantage of his clinic time in this episode, diagnosing a not-terribly-attractive man with cheating on his terribly attractive girlfriend. While she's strangely resigned to that – "I get it," she says – House adds that the cheating is of a dietary nature. The vegan nutritionist's boyfriend has been sneaking cheeseburgers. House moves in on the woman who has decidedly unsuperficial taste in men. 

Honey (can we call that irony, since honey isn't technically vegan?), as played by Piper Perabo of Coyote Ugly, is kinda dumb (Wilson: "She's 26." House: "With the wisdom of a much younger woman."). She's kinda pathetic. She's kinda flaky. But she's very, very pretty. That's all it takes to make her House's type, apparently.