In autumn, Sophora Town is shrouded in a thick fog that cannot be lifted. A bizarre murder breaks the silence of the town - a twelve-year-old girl, Shen Ni, died unexpectedly in the Sophora grove on the west slope. Before her death, she was obsessed with picking the copper bell from the Sophora tree, leaving dark brown tooth marks on her palms that were not her own, and stained with black tar debris.
The protagonist, Lin Yan, was raised by his grandfather in the mountains since he was a child. He learned the skills of trace investigation and identification of old objects. He brought a wooden sign with the word "quejian" engraved on him as a baby. Before his death, his grandfather asked him to follow the instructions when he met people related to the "quejian". As a consultant to Huai Town, Lin Yan was entrusted by the village party secretary to intervene in the investigation. He found that the copper bell in the girl's hand and the copper bell embedded in mud under the locust tree were a pair. They were engraved with the characters "que" and "jian" respectively, which coincided with her own wooden sign.
