In 1961, in Paterson, New Jersey, divorced mother Catherine Spages visits Father Tom with her two daughters, nine-year-old Karen and twelve-year-old Alice, who both attend St. Michael’s Parish Girls’ School. Karen is preparing for her First Communion, and Father Tom gives her his mother’s crucifix as a gift. A jealous Alice puts on a translucent mask, frightening Father Tom’s housekeeper, Mrs. Tredoni. Alice steals Karen’s porcelain doll, scares her, and threatens her if she tells anyone.
On the day of her First Communion, Karen is strangled to death in the church transept by a person wearing a translucent mask and a yellow raincoat, with her crucifix ripped from her neck. A nun locates Karen’s body, disrupting the communion ceremony.
After Karen’s funeral, Catherine’s ex-husband Dominick begins independently investigating her murder, while Detective Spina formally handles the case. Catherine’s sister Annie moves in to help her, though Alice and Annie despise each other. Catherine sends Alice to deliver a rent check to their landlord, the morbidly obese Mr. Alphonso, and he attempts to molest her. Annie is attacked by a masked figure. At the hospital, she claims that Alice tried to kill her. Alice is sent to a psychiatric institution for evaluation.
Dominick receives a hysterical phone call from someone claiming to be Annie’s daughter Angela, saying that she has Karen’s crucifix. Dominick agrees to meet her at an abandoned building. There, the figure stabs him before binding him with rope. Dominick sees that the killer is in fact Mrs. Tredoni, who chastises Dominick and Catherine as sinners over their premarital sex and divorce. After Dominick bites Karen’s crucifix off her neck, Mrs. Tredoni pushes him out a window to his death.
Catherine goes to visit Father Tom. He is not home but Mrs. Tredoni invites her in. She explains that when her own daughter died on the day of her First Communion, she realized children are punished for the sins of their parents. In her grief and madness, she devotes herself to the church. Father Tom arrives and tells Catherine that Dom has died. During Dominick’s autopsy, the pathologist finds Karen’s crucifix in his mouth, and Alice is eliminated as a suspect. Father Tom and Catherine go get Alice from the institution.
Mrs. Tredoni sneaks into Catherine’s apartment building. Mr. Alphonso wakes up screaming, as Alice had mischievously placed a jar of cockroaches on him while he slept. Mr. Alphonso encounters Mrs. Tredoni in the staircase and mistakes her for Alice. When he shoves her against a wall, she stabs him to death and flees. Detective Spina witnesses her running out without a mask on.
Mrs. Tredoni rushes to the church, where the police are stationed. Spina arrives too late to save Mr. Alphonso. At the mass, Father Tom denies Mrs. Tredoni communion. She stabs the priest in the throat as the police rush in. While Father Tom bleeds to death, Alice walks out of the church with Mrs. Tredoni’s shopping bag, and places the bloodstained butcher knife into it.
Linda Miller as Catherine Spages
Mildred Clinton as Mrs. Tredoni
Paula Sheppard as Alice Spages
Niles McMaster as Dominick “Dom” Spages
Brooke Shields as Karen Spages
Jane Lowry as Annie DeLorenze
Rudolph Willrich as Father Tom
Michael Hardstark as Detective Spina
Alphonso DeNoble as Mr. Alphonso
Gary Allen as Jim DeLorenze
Louisa Horton as Dr. Whitman
Tom Signorelli as Detective Brennan
Antonino Rocca as Funeral Director
Lillian Roth as Pathologist
Kathy Rich as Angela DeLorenze
Marco Quazzo as Robert DeLorenze
Ted Tinling as Detective Cranston
Sally Anne Golden as Policewoman
Patrick Gorman as Father Pat