It's increasingly hard to stand out in the murder mystery genre. There have been so many permutations of detectives, partners, time periods and settings that writers have to jump through hoops to find something new and unique. Rellik is a high concept thriller with an innovative gimmick.

The setup is pretty straightforward: Gabriel Markham (Games of Thrones / Fortitude's Richard Dormer) is chasing serial killer the Acid Murderer (Michael Shaeffer). However the narrative structure is anything but straightforward. Rellik is a backwards mystery. After every five or ten minutes of action we rewind into the past. During the opening episode in hours, by episode two we leap back even further.

A meticulous constructed puzzle from writers Harry and Jack Williams. The police already have their man, we know the killer's identity in the opening minutes. Or do we? Each reverse through time sheds new light on the how and why. There are regular revelations about character's backstories and motivations. But perhaps the cleverest part of Rellik is that the more we learn the more we question the end point. The facts constantly shifting and evolving, the details becoming ever darker and murkier.

Rellik is not the first thriller to use reverse chronology (Memento instantly springs to mind) but it still feels fresh and unusual. It's relentless grim, Jodi Balfour is an integral part of the team but this is tough guy macho police action (the unit also includes Ray Stevenson, Michael Wildman, Reece Ritchie and Kieran Brew) though there are some unexpected relationships revealed as the story develops.

Only two episodes were available to preview so it's hard to work out exactly how Rellik will fit together as a whole (which is part of the fun). Perhaps the real test will be how the Williams end a show told in such an abnormal way.

Rellik starts on BBC One, Mon 11 Sep, 9pm.