Viewers have been gripped by ITV drama The Pembrokeshire Murders which reaches its conclusion on Wednesday night.
The drama, starring Luke Evans, launched on Monday with 6.3million viewers glued to their screens and follows the investigation into two double murders that shook Pembrokeshire in the 1980s.
Police were unable to charge anyone for the brutal killings of brother and sister, Richard and Helen Thomas, and couple Peter and Gwenda Dixon and the cases remain unsolved.
That was until a renewed investigation in 2006, when both cases were reopened more than two decades after the first victims lost their lives.
The documentary features interviews with Detective Superintendent Steve Wilkins, the man who reopened the investigation, and forensic scientists involved in the case.
Viewers will see footage of the man behind the murders, John Cooper, as he is interviewed by police after new forensic evidence came to light.
The programme also investigates whether Cooper had another victim, a woman whose mysterious death was thought to be an accident.
'The Pembrokeshire Murders: Catching The Game Show Killer' will air on Thursday January 14 at 9pm on ITV.
Watch a preview of the documentary