In 1990 young wife Laura Fraser was murdered in her own house but the killer was never caught. 27 years later DS Katherine Stevens, helped by forensics expert Anya Karim, is given the cold case to find the culprit. At the same time divorced superintendent Elizabeth Bancroft and married sergeant Andy Bevan are trying to track down vicious drugs gang leader Athif Kamara, capturing his brother Daanish. Unaware of Katherine's affair with Andy, Elizabeth, who attended at Laura's murder, invites her to dinner with herself and her son Joe, the house being fire-bombed. Katherine approaches retired Charlie Haverstock who led the original Fraser investigation but gets no joy, before Elizabeth invites her to join her team, unaware of another death. Written by don @ minifie-1

After offering to help Katherine Charlie Baverstock is found dead as is Kamara's wife, a supposed suicide, though Elizabeth tells Katherine she was her informant. Her sister-in-law Zaheera agrees to help Elizabeth, who also approaches Daneesh in prison for his cooperation. Anya is concerned at the lack of forensic evidence retained from the Fraser case and goes to retrieve it at the holding bank but somebody else has got there ahead of her. Superintendent Walker is suspicious of Elizabeth's desire to help in the Fraser case whilst Katherine, her affair with Andy exposed, hopes a box of Laura's belongings given by her father Len can hold clues. Len himself believes Laura's widower Tim is hiding something, given his reluctance to reopen the case and then Anya makes a breakthrough. Written by don @ minifie-1

Katherine discovers not only that Elizabeth knew Tim Fraser but that he has recently visited her. Elizabeth admits that she covered for Tim after Laura's murder, believing he was innocent but atones for it by giving Katherine suppressed information. An angry Tim confronts Elizabeth, who later has a fight with Katherine. Meanwhile the Kamara case takes a dramatic turn. Written by don @ minifie-1

After an unsuccessful attempt to kill Zameera Elizabeth denies Anya telling her of her connection to the Kamaras and Katherine suspects Elizabeth killed Laura though Walker finds it hard to believe and closes the Fraser case. Katherine, however, is determined to press ahead and trap Elizabeth, who shoots her in a raid to capture Athif's gag. Now convinced of Elizabeth's guilt Walker interrogates her - and hears a stunning revelation. Written by don @ minifie-1