Creegan is on sick leave when a man who he helped convict for the murder of his wife and another woman is released from prison. Creegan was always unsure of the conviction, until the man made a full confession. However, when the murders start again, Taylor brings the suspect straight back into custody. Creegan then leads a one-man show to prove he was right. The suspect then commits suicide following interrogation, and a fourth victim is found shortly afterwards.

As Creegan continues to trail the killer, tragedy strikes as he leaves his hotel to find that the killer's next victim is none other than Rivers. As Creegan and Taylor struggle with the loss of their friend, Rivers' fiancé makes a plea for information as to who is responsible. Meanwhile, as the clues begin to piece themselves together, Creegan and Taylor then both come face to face with the killer and both have to restrain themselves from taking revenge for Rivers' death.

Creegan and Taylor come closer to identifying the killer when a fourth victim, headteacher Claire Logan, is found dead. They soon realise that victim Debbie Lewis' best friend, Lyn Sotherby, is none other than Susan Etchells in disguise, and they soon track her down to a disused hospital in Lincolnshire, where she has another victim ready and waiting. Creegan then puts himself on the line to secure the safety of the hostage, much to Taylor's dismay.