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.

Fanatical religious group leader Kenneth Trant discovers that his girlfriend Joanna is still alive and turns his attention to Dean, whom he trusted to dispose of her body.

With Joanna hospitalised, DS Beck extracts a confession from Dean while criminal psychologist Fitz tries to get at the truth.

He persuades DCI Wise to see Dean in his cell, but fears it may be too late.

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