The true story of how a serial killer was brought to justice is to be made into a three-part drama starring Hollywood actor Luke Evans.
Dracula Untold star Evans will play Dyfed-Powys Police officer Steve Wilkins who in 2006 reopened two unsolved double murders from the 1980s.
Microscopic DNA and fibres linked the murders to John Cooper who was already in prison for a string of burglaries.
Evans said it was a privilege to be playing the role in the ITV drama.
The star, who was brought up in Aberbargoed, Caerphilly county, said: "It's a huge responsibility for me as the drama depicts a true crime which to this day still affects the families of those whose lives were tragically taken."
The Pembrokeshire Murders has been adapted from the true crime book Catching the Bullseye Killer, written by Det Ch Sup Steve Wilkins and ITV journalist Jonathan Hill.
In 1985 Cooper murdered brother and sister Richard and Helen Thomas by shooting them at their remote mansion near Milford Haven, Pembrokeshire, and setting the property alight.
In 1989 he murdered Peter and Gwenda Dixon who he shot at close range on the Pembrokeshire coastal path near Little Haven.
In 2011 he was jailed for life.
The drama will be made by production company World Productions, makers of Line of Duty and Bodyguard.
Keith Allen, Owen Teale, Alexandria Riley, Caroline Berry, Oliver Ryan and David Fynn also star in the series.
Filming is set to begin this month.