Dark Heart follows DI Will Wagstaffe (Riley), a man tortured by his past, as he investigates the gruesome murder of Ray Collins. As the team investigate further, they learn Collins was a suspect paedophile who has previously been investigated by the police. Before long, Guy Dawlish, who was also investigated for child sex abuse, is brutally attacked in almost exactly the same way. With two unconvicted paedophiles attacked within days of each other, Staffe fears this could be just the start. (thetvdb.com)