Detective Sergeant Julie Cooper has been working undercover to crack a major drugs ring. With the drugs baron jailed, Julie thinks she can relax until she becomes the victim of a drive-by shooting that leaves her seriously injured and her aunt dead. Fuelled by grief, anger and guilt, Julie hires private detective Alec Tanner to help her track down the killers. Set in the fictitious English city of Havenchester, Double Jeopardy follows Julie and Tanner as they investigate a number of potential suspects, including a vicious gangland boss who is plotting to avenge himself on his cheating girlfriend. As their personal lives become increasingly entangled, Julie and Tanner find themselves in a race against time to uncover the truth and prevent more murders, including their own.