Joe (ALAN CUMMING) and Sally Therrian (JENNIFER JASON LEIGH) are celebrating their sixth wedding anniversary after surviving a yearlong separation. Despite their reconciliation, things are still rocky for the couple. Not only are they planning to move overseas and start a family, but Joe, a novelist, is also adapting one of his works - that's loosely based on Sally's life -- into a movie that he's set to direct, but hasn't cast his actress wife in the film.
Nevertheless, the two have decided to throw themselves an anniversary party where various friends, neighbors and business acquaintances are invited. Among the attendees are Jerry Adams (JOHN BENJAMIN HICKEY), the couple's business manager, and his wife Judy (PARKER POSEY);
Sally's good friend Sophia Gold (PHOEBE CATES) and her famous actor husband Cal (KEVIN KLINE); and filmmaker Mac Forsyth (JOHN C. REILLY) - who's directing Cal and Sally in his latest film - and his wife Clair (JANE ADAMS), who's a neurotic, new mother.
Others attending the party include Sally's best friend, Levi Panes (MICHAEL PANES), who's still getting over a recent breakup; Gina Taylor (JENNIFER BEALS), Joe's best friend and professional photographer with whom he may have had a relationship in the past; and Skye Davidson (GWYNETH PALTROW), the young actress Joe has hired to play the part inspired by Sally.
Then there are the neighbors Ryan (DENIS O'HARE) and Monica Rose (MINA BADIE) who don't get along at all with Joe and Sally due to the latter's dog, Otis, reportedly barking all night and keeping Ryan, who's also a novelist, from getting his latest work done. Although tensions have risen to the point of possible litigation, the four have decided to make an attempt at patching up their problems.
As the party and evening wear on and Ryan and Monica clearly feel like outsiders, various revelations and discoveries are made, some of which are fueled by various partygoers taking ecstasy.