Robin Ellacott receives a mysterious package by courier, which contains a severed female leg. Her boss, private detective Cormoran Strike, is not so surprised, but no less alarmed. In his past, there are four possible candidates for the identity of the sender - and each of the four is capable of unimaginable cruelty.

The police are concentrating their efforts on finding one of these four, but the further Strike goes, the more confident that it is this suspect nothing to do with it. Together with Robin, they are forced to take matters into their own hands and plunge into the abyss of the distorted psyche of the other three suspects. But a mysterious killer strikes again, and Strike and Robin realize that their time is running out...