After a young woman is found brutally murdered on a train, the police call in a brilliant but unstable psychologist to aid in the investigation.

Criminal psychologist Fitz is frustrated when another murdered woman is found and he is ordered off the case. Despite this initial setback, Fitz and DS Penhaligan are determined to find out the truth.

Problems between criminal psychologist Fitz and his wife Judith continue after Fitz is arrested outside his in-laws' house and taken to the station. There he meets Sean and his partner Tina, car thieves who embark upon a spree of violence.

Whilst on their spree of violence, Tina and Sean murder DS Briggs. Criminal psychologist Fitz turns down DS Penhaligon's offer of a bed for the night, but is then approached by Tina who asks him to accompany her to her flat.

Criminal psychologist Fitz interrogates Tina and realises that her psychological problems stem from her relationship with her family and she finds expression through provoking Sean.

Fitz investigates the fatal kidnapping of a 14-year-old boy.