Police novel of the Harry Bosch series. The veteran detective about to retire is assigned a rookie classmate to instruct her in the art of investigating, in the Open Case Unit: the case is the mysterious death of a mariachi, who dies ten years after receiving a bullet in the column. But the young detective tries to find out on her own who caused, years ago, the death of her friends in a daycare center. The two detectives join forces to resolve the two cases. The novel describes thoroughly, step by step, the work of the two policemen. It is well worn and maintains interest.