Schoolgirl Joanna Barnes, a member of a religious cult, is discovered to be having an affair with the married leader of the group, Kenneth Trant.

When confronted about it, he and the other leaders abduct her and the police reluctantly call in criminal psychologist Fitz to help find her.

When Trant's wife and sister discover that Joanna is pregnant they embark upon a vendetta against her that ends in attempted murder.

The case ends with a final showdown in the group's church, where things reach a destructive conclusion.