A young woman is found murdered near the city's red-light district. Her husband quickly becomes the chief suspect, but DC Mowbray has his doubts. Meanwhile, the detectives learn about the brutal murder of three prostitutes in nearby south Wales.

Tensions deepen between Mowbray and his wife, as the police launch their investigation into the latest killing. The murdered woman, a student, worked part-time at a pizza restaurant, where the detectives establish a link with the first victim in Wales.

The police pursue a number of leads, but Mowbray strongly suspects Robert Jackson, a delivery driver with a previous record of violence against women. Mowbray's boss disagrees, however, and the detective must decide whether to charge Jackson.

Another victim turns up, and morale among the investigating officers hits rock bottom. The stresses of the job force Mowbray to consult a therapist, but not before his actions drive Sally away from him. Adding to the pressure, the killer strikes again.

Mowbray takes himself off the case, goes on leave, and tries to patch things up with Sally and the kids. While he's gone, the police make an arrest. DCS Henderson believes he has his man but needs a confession to be sure.