The story takes place in Qinglan Town, a modern southern border town. This place is known as "the place where Yin and Yang meet". Every time there is a heavy rain, a group of strange hanging coffins will appear. In recent years, bizarre murders have occurred one after another in the town: the deceased all had purple complexions, wide eyes, and an ancient bronze coin engraved with ancient runes in their mouths. The police investigation yielded no results, and folk rumors suggested that the "blood evil" suppressed in the hanging coffin a hundred years ago had awakened. The protagonist, Lin Qiubai, is a folk culture researcher. Because he witnessed his mother being swallowed by a mysterious black fog when he was a child, he is obsessed with supernatural phenomena. He is invited to Qinglan Town to investigate the case, but he does not know that he is about to be involved in a mystery of yin and yang that spans a hundred years.
