S1, E1: A new witness comes forward with information about one of the country’s most controversial murder cases. David Morris, a builder with a long criminal record, has spent more than two decades in prison for the Clydach Murders but has always maintained his innocence. Now the police decide it’s time to open their files and review the case. This is the story of what started as a routine call to a house fire but became the biggest murder investigation in Welsh history.