The team are closing in on a convicted sex offender, but are missing a crucial piece of evidence; and newcomer DC Mark Rosen is set on the trail of a paedophile who may be carrying out his former cellmate's work.
Maurice befriends Mrs Cullen while Paul is placed under surveillance and the team wait for him to crack. Sally Brook takes drastic measures to escape Gibson. Ray and Neil are outraged but Ray implements his own form of justice.
The unit tracks a contract killer whose next victim has yet to be identified, and an escalating series of assaults on women at a nightclub.
The unit tracks an arsonist recently released from prison because of a police error, and a prostitute subject to violent rages who is likely to kill.