Catherine brings home Croatian Ilinka, one of several women rescued from human traffickers, and places her with elderly Polish friend Winnie before joining the house-to-house investigation of the serial killer who murdered three female victims. After his wife's death, Nevison reinstates Sean but Catherine suspects the young man of stalking prostitutes. She also attends Lynn's funeral, which Royce has been allowed to attend. He makes a scene and accuses her of killing his mother, a fact which does not please her superiors. Also present is Frances Drummond who, under an assumed name, has started teaching at Catherine's grandson Ryan's school. Returning home, Catherine argues with her sister, who has started drinking again, whilst John's attempt to end his affair with Vicky does not end well.

Catherine reconciles with Clare but her superiors see her as unstable and offer medical leave, which she rejects - accepting to see a therapist instead. Vicky's body is discovered but the murder of yet another prostitute allows John to suggest that both were the serial killer's victims. His marriage is on the rocks anyway. Catherine is shaken by the apparent suicide of one of Ilinka's slave-masters, whom she had tasered and arrested but who had been released on bail. Ilinka thinks he has been silenced. Meanwhile, deceived by Royce's lies, vulnerable, besotted Frances Drummond is encouraged to ruin Catherine's life.