When the body of teenager, Julie Ann Collins, is found in the underground car park of a Hackney housing estate, probationer WPC Jane Tennison becomes immersed in her first murder investigation. Jane’s superior DI Bradfield believes that the victim’s drug addict boyfriend, Eddie Phillips, is involved in the crime, tracking him down for questioning. However, despite Bradfield and DS Gibbs being convinced that he is hiding something, the interview is cut short when Eddie collapses and is sent to hospital. Meanwhile, with his release from prison imminent, renowned criminal Clifford Bentley is preparing for an upcoming bank robbery that he and his family are carrying out for gangland kingpin Clay Whitely. With information reaching him that his wife, Renee, has been attacked as a warning from Whitely though, he becomes nervous. At home, Jane’s mother voices concerns about Jane’s chosen vocation and wishes she were more like her younger sister, Pam, who is about to be married. However, determined and ambitious Jane is adamant she’s going to help catch the killer though.

The police delve deeper into the murder of Julie-Ann Collins, setting their sights on the driver of the car the victim was last seen climbing into. However, as the hunt gets under way, relations become strained between Jane and DI Bradfield when she walks her drunken boss home one night. Meanwhile, Clifford Bentley is fuming over the attack on his wife by gangland kingpin Clay Whiteley and launches a revenge attack - putting his family's criminal interests in jeopardy.

Following the revelation of the red Jaguar in George and Mary Collins’ garage, the pair protest their innocence about their daughter’s final days. The case against them hardens when forensics officers discover further signs of violence against Julie Ann in their home. With the timeline of Julie Ann’s injuries not adding up, Jane pursues a witness who say Eddie visited George Collins the night before Julie Ann’s death. Backed into a corner, George makes a confession that throws an unexpected light on his daughter's death. Meanwhile, Clifford Bentley is released from prison and returns home to a hero’s welcome. Alongside John and David, Clifford is ready to put the final plans in motion for the bank robbery, but café owner Silas is getting cold feet.

Following his arrest, a badly beaten Terrence O’Duncie is brought into the station. With Gibbs on the hook for his attack, Bradfield asks Jane to make a decision with huge repercussions for her future. The case escalates when Eddie Philips’ body is discovered in the canal, and Bradfield suspects they’re looking at a double murder. He questions O’Duncie about his connections with Eddie and Julie Ann, but his progress is halted when O’Duncie’s solicitor files an official complaint against Gibbs. Meanwhile, Clifford Bentley and his sons start digging from the café to the bank, but they risk getting caught when David fails to notice the police presence outside as he’s high. Silas manages to reassure the police that they’re carrying out refurbishments but Clifford and John confront David about his worsening drug habit and unreliability.

Jane plays the radio recordings to Bradfield who, sensing a chance to get his revenge on Clifford, diverts the team to carry out surveillance of the Bentleys, despite orders from his superior officer to stay focused on the murder case. Reluctantly taking a day off to attend her sister Pam’s wedding, Jane calls into the station to check in with Kath, learning that her tip-off has led to a huge surveillance operation. Determined to be part of it Jane rushes off, still in her bridesmaid dress. Meanwhile, one of Clifford’s team betrays him, and Bradfield soon uncovers the exact details of the Bentleys’ bank heist. Ignoring the disapproval of his colleagues, as well as Jane, Bradfield is determined to catch them in the act.

In the aftermath of the explosion at the bank vault, the police operation descends into pandemonium and panic. As Jane arrives at the scene, she is met with devastating news. Renee gives David cash and tells him to find somewhere to lay low. Later, Clifford reaches the flat and tells Renee the terrible truth about John. Renee refuses to believe him. The police station is numb with shock, but Harris rallies the troops into a manhunt for Clifford and David. A distraught Renee refuses to help and is arrested. Jane and Gibbs, investigating the connection between Julie Ann and the Bentleys, question Renee who finally breaks down and admits David’s relationship to Julie Ann. At a search of the Bentley lock-up, Jane uncovers evidence that it was where Julie Ann was killed. The Bentleys' van is searched and a small silk bow discovered which matches Julie Ann’s bra. The police manhunt ramps up with David Bentley now as their prime suspect. And Jane finally gets to the truth of what really happened.