DCI Cassie Stuart (Nicola Walker, Last Tango in Halifax) and DI Sunny Khan (Sanjeev Bhaskar, The Indian Doctor) face an impossible cold case. A lawyer. A nurse. A schoolteacher. A police officer. These four suspects are the pieces of the puzzle. But as Cassie and Sunny put this picture together, the more blurred it becomes. The investigation will question their assumptions about the most damaged and destructive in society. When a victim becomes a criminal, is punishment the same as justice?