Major and Carver reunite, but tensions remain high. When a police officer is murdered, Carver becomes hell-bent on solving the case, Major has an epiphany and resolves to become a better man, and both detective inspectors are out to prove themselves.
With a serial killer at large, Major and Carver call on the help of forensic psychologist Professor McAllister. Parfit worries about Major's AI updates.
Chalmers, the former police commissioner who has plagued Major since the day he was reanimated, faces trial. With Major busy testifying, Carver is running out of time to decipher the latest clue and save the killer's next target.