As DI Hudson's new investigation unearths serious flaws in the original murder investigation, those who were closest to Tara are forced to explain away credible motives for wanting to kill her. Relationships are strained to breaking and damaging accusations fly when David confronts his brother and sister-in-law over access to his children.

After seven years in prison for the murder of his wife, David Collins is released due to a technicality. The police now need to reopen the case in search for the murderer.

Matthew Taylor, a 16-year-old school boy was brutally murdered in the quiet Lake District. Five years later the accused is found not guilty and released from prison, but who did kill him?

As Sally begins a confident return to work, the police question Anna Stamp - what is she hiding, and more importantly what are Matthew’s parents covering up? Karen grows increasingly paranoid over Sally and Sam.

As Sally and Sam grow closer, the police investigation turns to Gary Walker, but what is his connection? Meanwhile, Bethany's link to Matthew comes to light as Karen admits a damning secret.

With Karen still in police custody, Bethany takes matters into her own hands - making a crucial discovery and forcing a confession. Braithwaite and his team continue their search for more evidence. Sam and Sally come to a decision.

Alice and Rob's relationship continues to disintegrate as evidence under questioning incriminates them further, and the children grow closer to David. Meanwhile, Tom's attempts to save his marriage are destroyed by his subsequent arrest, and forensic evidence throws new light on David's original conviction.

David is the subject of a sensational tabloid story, and struggles to explain things to his children. Tom is confronted by his ex-wife, who demands his help. Last in the series.