Creegan and Taylor investigate a serial killer who is sending reports of each of his murders to a local journalist, David Laney. When Rivers tails the prime suspect to a shack in the woods, his hesitation results in the death of another victim. However, with the killer in custody, Creegan is surprised to receive another message stating another murder is about to happen. The search of a warehouse yields another body, that of a local MP.

Taylor heads to Romania to collect a child whilst remaining undercover, and as the ring is threatened to be blown apart, the suspects make a break for it. As baby trader Reggie Hansen agrees to give evidence in court, Creegan is left devastated when Annie Jordan is shot and murdered in the passenger seat of his car by maniac Mark Hawkins. Creegan then has to choose whether or not to get justice for Annie or do the right thing and bring Hawkins in to custody.

Creegan realises that Laney may have been the killer all along, and puts surveillance on him. However, when he slips out of sight, he confronts an innocent café owner who is later found dead, with her throat having been cut. Laney then kidnaps Taylor and takes her back to the shack in the woods. Creegan and Rivers arrive to find a hostage situation, but the guilt over his hesitation the first time leads Rivers to jump in and shoot Laney dead.

Creegan and Taylor investigate when a young boy is snatched from the back garden of his parents' house. The search leads to Annie Jordan, who claims to be the boy's biological mother – and that she sold the boy to a dealer who internationally trades in children. As the team discover links to a paedophile ring, Creegan has to deal with personal tragedies of his own when a relative of a murder victim tries to kill his ex-wife and children by setting fire to their house.

Creegan and Taylor investigate links between a number of dead bodies found in white body bags, having been delivered to the homes of the victim. The trail leads the team straight to the aftermath of the Bosnian war, where all of the victims played a part in the clean-up and salvage operation. Rivers, angered that he had the prime suspect in his clutches, attacks him when the team finally catch up with him. However, a shocking revelation blows the case wide open.

Rivers goes it alone to try and track down Keller, but the killer's one-man rampage results in two further murders and two further attacks, including his wife and partner. When a personal note is delivered to the station, and the family of one of the young murder victims participate in a press release, Keller goes on the rampage with a gun at the young boy's funeral. During a shootout, Rivers is gunned down. Taylor wonders if she pushed him too far.