A job in the Prison Service is not for everyone. The training is hard, the cells are bleak and a thick skin is needed. But for Nell Lewis, helping prisoners is something she cares about deeply, and when she's promoted into a new post as governor of HMP Brackerley in Yorkshire, she's tasked with transforming the renowned run-down facility into a modern, open prison for women. Just as Nell is settling into her new role, events take a dark turn when a man's body is discovered in the prison grounds. The mystery deepens still when one of their female inmates goes missing, ensuing a search across the country.