Mary Bradford (Mischa Barton) is the newest girl at a preparatory boarding school for girls. She makes friends with her roommates, Paulie Oster (Piper Perabo), and Tori Moller (Jessica Pare). Mary witnesses a kiss one night between her roommates and wonders if they are actually lovers and not just friends. Their relationship evolves until Tori’s sister Allison (Emily VanCamp) finds them in bed after they have spent the night in it together. Tori wants to end things at that point because of the possible reactions of her family and her classmates, but Paulie does not. Paulie becomes unstable mentally because of this rejection.