DI Dave Creegan is paired with DI Susan Taylor on his first day to investigate the disappearance of three young schoolboys who have all been snatched in broad daylight. Creegan discovers a link with two boys who disappeared in Stuttgart some three years previously, but surveillance on his prime suspect fails to yield any information. Taylor is concerned that Creegan is putting all his eggs in one basket and efforts to investigate other lines of enquiry.

A satellite surveillance van picks up images of the young boys held in an airtight room. Creegan realises that time is running out, and when prime suspect Ronald Hinks gives a silent interview, he realises he may have to break the rules to secure the boys' safety. As Taylor organises a house-to-house on an abandoned estate, Creegan kidnaps Hinks' dog and puts him onto a scent, which leads Creegan straight to the crime scene. But is he is too late?

A group of patients who are all on the same ward at a local hospital die within minutes of each other. When the cause of death is found to be an overdose of drugs, and each of the victims has the tattoo 'let me go' stencilled onto their back, Creegan and Taylor investigate the hospital cleaner, Carl Burgess, who is found in possession of items belonging to a senior doctor. Creegan is left unconscious after being attacked at home, but who is responsible?

The investigation's attention turns towards locum Julie Carney following the attack on Creegan. When she commits another murder in Wales, Creegan realises that he needs to set a trap to lure her home. Rivers and Krietman's pursuit of an unstable Carl Burgess results in Burgess trying to kill a patient, and then electrocuting himself, from which he dies of his injuries. When Julie Carney resurfaces, Creegan is forced to watch on as she tries to commit suicide.

Creegan and Taylor reel in convicted killer Justine Barber, whose crimes from some years ago mirror the exact methods used to commit the current murder. When she leads them to prime suspect Leonard Stoker, a chase ensues and Stoker is arrested. Creegan has no choice but to file a report on Kreitman. Enwright refuses to press charges on the grounds of no evidence, but leaves Kreitman without a job. Kreitman, upset at the result, goes on the rampage.