Following the dramatic climax of season one, rookie P.C. Lizzie Adama returns to her London police station, where she finds herself fighting to protect a mother and daughter in peril. D.S. Sarah Collins, having transferred to Homicide Command, reopens a cold case involving a missing schoolgirl that leads her to cross paths with Lizzie again. D.I. Kieran Shaw wants to recruit D.S. Steve Bradshaw for a specialist task force targeting a major organized crime figure but must convince Steve he can be trusted.