When the remnants of a body are found hidden in a river, DCI Cassie Stuart and DS Sunny Khan are faced with an impossible investigation. David Walker disappeared in 1990 at the age of 34. Only scraps of potential leads remain, but relentless work leads Cassie and Sunny to four people. Each has a connection to Walker, and a painful secret that might have driven them to murder. 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.