Happy Valley viewers were quick to point out the 'obvious' blunder as they tuned into watch Sergeant Catherine Cawood take on her final mission, which saw her have one last showdown with dangerous crook, Tommy Lee Royce.
BBC One viewers couldn't quite believe show writers had missed such a pivotal part to the story as they watched in horror as Tommy Lee broke into Catherine's home, where he attempted to end his life with a concoction of pills and alcohol.
The chilling scenes saw the escaped killer, who had raped Catherine's late daughter, sitting at her kitchen table flicking through her family photo albums with the pills and booze alongside him.
