A Confession is the gripping ITV series based on real-life events, and the investigation into the disappearances and murders of Becky Godden-Edwards and Sian O'Callaghan.
DS Steve Fulcher, who is portrayed by Martin Freeman in the series, was in charge of the case and believed he would find Sian alive - while Becky's murder was yet to be discovered at this point.
Sian vanished after a night out in 2011, and it was only while investigating her disappearance that Fulcher made a link between her and missing Becky, who had vanished eight years prior.
Serial killer Christopher Halliwell confessed Sian's murder to Fulcher and showed officers where he had buried her body, before asking them if they wanted "another one".
With this being eight years on from Becky's death, how was what happened to her solved and how did Fulcher make the link between the cases?
After having sex with Becky in January 2003, he strangled her before burying her body in a field - while her head was missing from her corpse.
The murder would remain unsolved until 2011, when Fulcher confronted suspect Halliwell over a different girl's disappearance.
He quizzed Halliwell over Sian's whereabouts, believing her to be alive, but the killer confessed she was dead and took him to where he had buried her.
It's then that he offered to show the detective the place another of his victim's was buried, while not revealing the name of the girl
Fulcher managed to link Sian's case to Becky's due to similarities in events, and believing she could be the girl who Halliwell had not identified he stepped up the investigation to solve the case and get justice.
The manner in which Steve gained Halliwell’s confessions breached police procedure though, by failing to caution him and denying access to a solicitor.
This almost derailed the court case against Halliwell and called into question one of the most important principles of the criminal justice system - but it was also Steve's actions with Halliwell that led to Becky's murder being discovered and her case solved.
Halliwell was sentenced for the murder of Becky in September 2016, while he was already serving a life sentence for killing Sian.
A Confession continues Mondays at 9pm on ITV.
