Upon taking her vows to become a nun, Sister Sarah is abused, brainwashed and also drugged into submission by the corrupt clergy. On the verge of her own death from a lethal dose of drugs, Sister Sarah receives a message from God telling her to take vengeance on all those who did wrong to her. Armed with God's will and an arsenal of big guns, she dispenses Judgment Day on her former tormentors. When the church hires the merciless motorcycle gang "Los Muertos" to track down and to kill her they soon realize that this sister is one bad mother.

Things go horribly wrong when Catherine and Rebecca, two Catholic School girls, knock on the wrong door while selling Religious paraphernalia.