Hayley Atwell stars as an obsessive police officer in this TV miniseries. Set across three episodes in 1985, 1997 and 2013, rookie WPC Denise Woods (Atwell) hunts for the killer of 15-year-old schoolgirl Amy Reid (Eloise Smith). As she navigates the law enforcement ranks from constable to superintendent, Denise must fulfil her own personal desire to resolve her first case while acting against the strict instruction of her superiors at Brixton police station. As her work threatens to consume her, Denise struggles to achieve balance in her home life with husband Ray (Richard Coyle) and daughter Charlotte (Ruby Thomas).