Following the shocking discovery of a 15-year-old girl's body, DI Dale Carter fixates on his prime murder suspect, Ryan Kelvin. However, Jack's personal connection to Ryan presents a conflict of interests, leading Thomas to replace him on the case with forensic scientist Helen Ferguson. But in his quest for the truth, Jack is instinctively drawn into the investigation, alienating him from Nikki and the team. Hannah, the distraught best friend of the victim, becomes consumed with grief and guilt over the murder, leading her to take drastic action.