Playing a fetching psychopath, Parker Posey puts a serrated edge on the mostly innocuous The House of Yes, a comedy of early-80s manners that coops up three siblings, a matriarch, and an outsider in the family home over Thanksgiving night while a storm rages outside. Posey is Jackie-O Pascal, a well-practiced Jacqueline Onassis fetishist who's dangerous when she's unmedicated. She can't be accused of good taste -- she pays homage to the Kennedy dynasty by dolling herself up in a pink suit and pillbox hat, a la the more famous Jackie O. At a costume party, she once added a blotch of ketchup and a dollop of macaroni to the outfit to, um, accent the ensemble with mock blood and brain matter from a certain assassinated president.

It's not that our Jackie-O is simply an American history buff with a grisly bent. Also among her issues is a longstanding sexual relationship with her twin brother Marty (Josh Hamilton), who is helpless to resist her charms. (They reenact the Kennedy assassination together, Marty sitting upright and waving vacantly.) The soaking-wet outsider is Leslie (Tori Spelling), whom Marty has brought home for the holiday to introduce as his fiance. (Daggers from Jackie's eyes, natch.) But before the night is over, Marty and Jackie will pair off to, um, discuss old times. Meanwhile, awkward younger brother Anthony (Freddie Prinze, Jr.) already has designs on Leslie. As the matronly Mrs. Pascal, Genevieve Bujold hovers disapprovingly over the proceedings.

Wackiness ensues, leading up to the third-act introduction of a loaded gun into the housebound milieu. (If you guessed this was based on a stage play, you're absolutely right.) The House of Yes is fitfully funny, but I can't help but think it missed an opportunity to be truly bizarre. Although it's been compared to the bold work of Noel Coward, Harold Pinter, and Tennessee Williams (!), it retreats too readily to the shelter of self-conscious absurdity. The movie saves itself from its own staginess by being aggressively artificial, and nobody is better at playing that game than Posey, who can imbue even the most honeyed line with the flutter of latent wickedness. The result is a black comedy that's oddly agreeable. The outrageousness is parlayed with a wink, and the campy performances reflect the melodrama that seems to infect every corner of the Pascal family's daily life. Only Spelling, doing an uncanny imitation of a fish out of water, doesn't seem to be in on the joke.