For all its talk about sex, incest, insanity and the gory details of the Kennedy assassination, Mark Waters' adaptation of Wendy MacLeod's play doesn't really amount to much more than a lurid, thoroughly enjoyable little pot-boiler. Jackie-O (Parker Posey), the cracked, spoiled daughter of a wealthy Washington, DC matriarch (Genevieve Bujold), has two obsessions in life: Jacqueline Kennedy Onassis and her twin brother Marty (Josh Hamilton) whom she loves... a lot. One dark and stormy night, Marty arrives home for the Thanksgiving holidays with a surprise on his arm: his somewhat dim fiancee, Lesly (Tori Spelling). This all comes as a terrible shock to Jackie-O, who's only just come home herself after a stint at the sanitarium, but it's nothing that can't be fixed with a little psychological terrorism and a quick game of Jack and Jackie, starring Marty and herself. It's all about as morbidly fascinating as peeking in on your neighbors and catching them at their worst, but thanks to a strong cast, it hums along quite nicely. Posey has become so good at playing herself that she's great fun to watch, sneering her way through the unsavory doings with acidic relish. Bujold is as good as ever, but the real surprise here is Spelling: Slack-jawed and dewy-eyed, lids forever at half-mast, she's perfectly cast as a lamb among wolves, and her naivete is strangely affecting.