Après que le sergent Ian Durrant, policier hors service, ait trouvé un homme mort au volant de sa camionnette, les détectives font le lien entre la victime et une femme qui a été tuée pendant sa garde à vue. Le détective Rob Brady étant celui qui l'a découverte morte, cette affaire l'affecte profondément. Lorsque la stagiaire Billie Fitzgerald trouve un lien avec le meurtre d'un jeune policier, David Bradford soupçonne que le tueur pourrait être un officier de police.

When schoolboy Luis Moretti is found dead in a lake, the detectives learn of a potential connection to the recent suicide of a young girl. Meanwhile, DS Vivienne Cole tells David that she believes Detective Chief Superintendent Mulgrew was behind the threat to Rob's family, and she reveals her past relationship with the chief.

After a locksmith is murdered, Billie recognizes the victim and learns he was a witness to her father's death 10 years earlier. The investigation brings her face-to-face with her father's killer and forces her to wrestle with her personal and professional ethics. Vivienne pleads with her ex-husband to do the right thing, but he is afraid they're both in danger.

A body found in a suitcase is identified as a man who has been missing for two weeks. When the team inform his widow, Cassidy, she seems unaffected and points the finger at her brother-in-law, Charlie. But Charlie claims that Cassidy is a control freak whom his brother planned to leave. Is Cassidy a cold fish or a ruthless killer? Meanwhile, David tries to convince Mulgrew to reveal what he knows.