Kathryn Merte (Amy Adams) is the manipulative, cold-hearted daughter of social climber Tiffany Merte-Valmont (Mimi Rogers). Tiffany has just married again, and Kathryn is not getting along well with her new stepbrother Sebastian (Robin Dunne), who is just as skilled in the venomous art of social gamesmanship as Kathryn. Together they negotiate the tricky paths of sexual and personal power at their upscale private high school.