When the remnants of a body are found hidden in a river, DCI Cassie Stuart and DI Sunny Khan are faced with an impossible investigation. There are four suspects - they are the pieces of the jigsaw Cassie and Sunny must solve. But the harder they try to put this picture together, the more blurred it becomes. It's a case that will test their relationship in unexpected ways, and question their assumptions about the most damaged and destructive in society. When a victim becomes a criminal, is punishment the same as justice?