In what we must assume is the past, a group of girls at a catholic boarding school bond in friendship and orneriness. They're all free spirited 'bad girls' and grate against the sensibilities of the sisters that run the school. Sister Ursula is their nemesis; she's strict and holds to the old school rules of hard punishment which the girls see as cruel and unusual. Eventually they have all they can take and so they decide to take action; bad things happen, the sister dies and the girls hide her body.
Cut to the future: