This book is divided into two volumes:
The first volume tells the story of the northwest wilderness in the early years of the Republic of China. Detective Lu Shen sneaks into the troupe to investigate a bizarre murder case involving a shadow puppet troupe. He is shocked to discover that the shadow puppets are all made of human skin by a magician in the late Qing Dynasty. They are evil and bloodthirsty. The underground blood pool is frightening, and the gravekeeper appears mysteriously. Although he survived by chance, a cinnabar mark of unknown origin was branded between his eyebrows. After returning to the city, he was haunted by nightmares and his shadow showed red marks. Only then did he realize that evil spirits were following him like a shadow, transcending reality and reality, marking him as a prisoner who would never escape.
The second volume tells the story of Lin Ke, an orphan who was adopted by a gloomy old blind fortune teller before and after liberation. He was forced to learn the weird bone-touching technique since he was a child, leaving a deep psychological shadow. As an adult, he became a forensic doctor who firmly believed in science. However, in a shocking serial bones case, he discovered an "ancestral mark" originating from an old blind man inside the victim's skull that he never wanted to see again.
In order to save himself, he was forced to return to the dark place deep in his memory, go deep into the desolate Gobi desert in the northwest, and encountered horrific phenomena and existences that science could not explain. In the end, the horrifying truth emerged: the bone-touching technique he learned was actually connected to a horrific cycle of using bones as debt and feeding things behind the "door", and he himself might have been the carefully selected "feed" from the beginning.
