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.
DI Will Wagstaffe is called to investigate a gruesome murder, but they soon learn that the victim was arrested two and a half years ago on suspicion of sexually assaulting his young step daughters.
The detectives continue to look into a string of attacks on a series of people who were marked as paedophiles but never convicted, although Wagstaffe is frustrated by the eerie wall of silence from the victims' families. To make matters worse, a web of deceit begins to unravel - leading the DI to a disturbing conclusion.
DI Will Wagstaffe and his team investigate the mysterious death of a young nurse on the London Underground. Whilst CCTV reveals the victim fleeing an invisible assailant, forensics find a DNA link to a missing teenager presumed dead for seven years. Aided by his new team DS Rob Mullan, DC Ray Monk, DC Annie Webb and pathologist Dr Luke Paul, Will unearths a bond of secrets and betrayals which leads him straight into the dark underbelly of the city.
As the team delves deeper into the poisonings, it quickly becomes clear that those responsible have a powerful influence. The pressure builds for DI Wagstaffe to find buried links between Sofie Cerna and Nick Kyriacou, but when the investigation veers close to home, he finds himself making his sister's fiancé Paulo an offer that could have far-reaching consequences.
A young woman is found murdered in an East London church, and DI Will Wagstaffe must establish if it's the work of her recent stalker or if the answer is more complicated.
As the team delve deeper into the circumstances surrounding Suzy's death, details of her torrid emotional state reveal a surprising new line of enquiry.
