Ambitious DI Joseph Chandler is assigned an open-and-shut case, the killing of a woman in the East End of London. Get a quick result, he is told, and you will get the promotion you have been waiting for. Unfortunately for him, however, things don’t turn out to be so straight forward. The investigation quickly runs out of suspects until Edward Buchan, a renowned Ripperologist, draws the police’s attention to the similarities between the Jack the Ripper killings in 1888 and the modern-day murder that Chandler is investigating. The race begins to catch the copycat killer before he strikes again.

Chandler continues to clash with his team, led by the cynical DS Miles. Further suspects lead to dead-ends as the detectives attempt to penetrate the conspiracies and myths that surround the legend of Jack the Ripper. Frustrated, Chandler pins his hopes on trapping their latest suspect, a solider named Leary, but the operation goes horribly, tragically wrong.

The final act begins – the Ripper must kill one more victim to complete his re-enactment of the 1888 murders. Chandler is near to breakdown as he struggles to find an answer. Forensics and CCTV are useless, and the team is forced to rely on its instincts, hoping that the past will provide some clue to the killer’s identity. But time is ticking away, and history tells us that Jack the Ripper was never caught.

The acclaimed police drama series returns for a brand new three-part series. Set in East London, the programme focuses on the work of a team of officers whose personal tensions must be put aside if they are to solve a vicious copycat crime. DI Chandler and his team investigate a series of brutal murders and maimings, all of which stir up uneasy feelings for DC Miles. After the killings which mirrored Jack the Ripper's slayings, local history expert Buchan suggests that there may once again be a copycat killer at work - this time, the deaths seem to recall crimes committed by the Kray twins in the 1960s. Miles and Chandler refuse to believe Buchan's theory because the Krays both passed away years before - but is Buchan on the right path? As the investigation becomes more intense, the members of the team find themselves delving into some very dark places, and DI Chandler must tackle his personal demons if the police are to solve the case.

Reeling from Slasher’s death and with absolutely no leads, Miles informs Chandler that the copycat killer has struck again - just as Buchan predicted. A man called Billy Bunhill is shot dead in a former Kray haunt - his murder mirroring George Cornell’s killing by Ronnie Kray. A barmaid offers up a name - Jimmy Kray. The team is stunned - does a real Kray exist? An interview with Jimmy’s mother, Angie Brooks reveals a former relationship with Ronnie Kray which resulted in identical twins - Jimmy & Johnny. These twins epitomize everything their father stood for - wanting to realize their father’s dream and create a ‘Federation of Crime’, Jimmy even has a boyfriend, (‘Blonde Boy’) and is clearly insane. Dropping Dukes from their enquiry, the team focuses on the twins but is frustrated when Cazenove believes them to be nothing but small time thugs. Chandler’s dogged pursuit of the twins quickly puts both himself and his team in danger. He becomes incensed when at every turn the twins are one step ahead. Chandler realizes that he can no longer trust anyone - even his colleagues - both Fitz and Kent appear to have been turned by the Krays. Not even snout, Jack Cheshire, seems able to help Chandler and with little to go on, his OCD worsens. A suggestion from Buchan to meet the twins results in a massive shoot out - is there any way that Chandler will be able to bring down the Krays?

The shoot out has an enormous impact on Chandler and he turns to drink - realizing it helps numb his OCD. Nothing, however, can prepare Chandler for the sight of McCormack, whose dead body is found hanging in his garden shed. McCormack was the ‘insider’ but was unable to cope with the pressure of betraying his colleagues - this means Kent is instantly welcomed back onto the team. With Commander Anderson’s help, Chandler hides the team away in Buchan’s House ensuring more privacy for their investigation. Anderson provides them with a suitable cover story but can only give them 3 days to bring down the twins. With the clock ticking and little to go on, Buchan reminds Chandler of former Inspector Nipper Read’s mantra, ‘attention to detail’. The team kick-start their investigation, helped in part by Jack Cheshire - whose allegiance Chandler can never be sure of. Working in such a close environment tensions boil and Buchan is forced to reveal his own investigations - into the disappearance of Miles’ father. The revelation not only stuns Miles but also helps suggest a new take on the current investigation, linking Ronnie’s penchant for young boys to Jimmy’s ‘Blonde Boy’.