Twins Jackie-O (Parker Posey) and Marty (Josh Hamilton), whose father disappeared the night Pres. John F. Kennedy was shot, have an unusually intimate relationship that blows up when Marty comes home one Thanksgiving with a fiancée (Tori Spelling). The mentally unbalanced Jackie-O -- who thinks she's Jackie Kennedy -- suddenly flips into a jealous rage, and all her mother can do now is hide the kitchen knives and hope for the best.