DI Will Wagstaffe, known as Staffe, is at London City airport when his colleague, DC Josie Chancellor (Anjli Mohindra) calls him to tell him there's been a gruesome murder. Being the workaholic he is, Staffe abandons his personal plans and heads to the scene of the crime.
Staffe, along with Chancellor, DS Dave Pulford (Kobna Holdbrook-Smith) and DS Rick Johnson (Tom Brooke), are confronted by a horrific scene – Ray Collins (Mark Fleischmann), a man in his mid thirties, has been tied to his own bed, choked and severely mutilated.
As the team, based at Leadengate police station in London, investigate further, they learn Collins was arrested two and a half years ago on suspicion of sexual assault of is own daughters, Holly and Jasmine, who were just nine and eleven at the time. He was remanded in custody for three weeks but there wasn't sufficient evidence and Collins was released.
As Staffe and his team delve deeper they speak to Collins' ex-wife, Debbie Collins (Simone Kirby), who is mother to his daughters. She admits she is relieved to hear of his death; grateful that no other child will go through what hers did.
Soon after Collins' death, a lawyer, Guy Dawlish (Nicholas Asbury), is brutally attacked. The style of attack is similar to the way in which Collins was killed – he was tied to his bed using knots that are exactly the same as the ones used to restrain Collins. The similarity doesn't end there – Dawlish was arrested two years ago following allegations of child sex abuse. There was insufficient evidence so he wasn't charged.
With two unconvicted paedophiles attacked within days of each other, Staffe fears this could be just the start…
Whilst devoting his life to his work, Staffe also battles personal demons. He's haunted by the unresolved murder of his parents.
Staffe has an on-off romance with Sylvie (Miranda Raison), but his closest relationship is with his sister Juliette (Charlotte Riley) and seven year old nephew Harry (Joseph Teague), who come to stay with him when Juliette has troubles with her boyfriend Paulo (Edward Akrout). With no parents and no significant partner of his own, Juliette and Harry mean everything to Staffe, so when he fears Paulo is up to no good, protective Staffe takes matters into his own hands…