A troubled English girls' boarding school becomes the setting for an obsessive and destructive rivalry when a glamorous, mysterious new pupil arrives and captivates the swimming team's charismatic but deeply unstable coach. The teacher's unhealthy fixation on the newcomer gradually unravels her carefully constructed persona and exposes the dark, delusional nature beneath her surface charm. As jealousy and desire spiral out of control, the consequences prove devastating for everyone involved.