Thoughts on, and a place to discuss, the plot details we can't reveal in our review.
Okay, the movie being riffed on can finally be revealed…
Alfred Hitchcock’s Psycho. Thieriot is the Norman Bates of this scenario, the sweet-natured, socially awkward occupant of a house that’s big and full of ghosts. It turns out that he’s keeping his still-alive little sister under lock and key in the cellar, feeding her chicken soup and doping her up whenever she attacks him. It seems the boy feels some responsibility to take care of the girl, since he was present the day she had an accident that switched her brain from “adorable imp” to “psychotic bludgeoner.” So yes, it’s a little twisted for Thieriot to treat his sister like a rabid pet, but it’s a little kind, too, until…
… Another twist where Thieriot stops the girl from killing a couple of necking teenagers by snapping her neck. Only wait, wait, wait, there’s a second twist where it turns out the now-dead girl isn’t his sister, but one in a series of like-aged girls that he abducts, keeps in the cellar, and fits with blue contacts to look like his sister. Not too shabby, right? They’re the “mother” in this Psycho scenario, and the film even ends with Thieriot in a mental ward, albeit without some stuffy psychologist explaining his condition in the coda.
One big problem with these twists: It makes the abhorrent actions of the townspeople completely justified. Thieriot is, in fact, the boogeyman they make him out to be, so the unctuous jock who forces himself onto Lawrence and assaults Thieriot outside the high school could fairly be seen as heroic. And on the other side, the decent cop who does everything he can to treat Thieriot sympathetically is totally in the wrong. Let that be a lesson to you, folks: If a family is slaughtered and the sole survivor moves into the murder house, best to follow your instincts and burn the place to the ground with him/her in it.