In the middle of a hard-won morning nap in the basement of police headquarters, Carl Mørck, head of Department Q, receives a call from a colleague working on the Danish island of Bornholm. Carl is dismissive at first, but then he receives some shocking news.

Carl then has no choice but to lead Department Q into the tragic cold case of a vivacious seventeen-year-old girl who vanished from school, only to be found dead hanging high up in a tree. The investigation will take them from the remote island of Bornholm to a hidden cult, where Carl and his assistants must stop a string of new murders by a skilled manipulator who refuses to let anything-or anyone-get in the way.