During the Southern Song Dynasty, the former county magistrate of Tonggu County used the "River God" as a cover to secretly kidnap children for his own selfish interests. The people were in a panic and believed that sacrificing children to the "River God" could calm the disaster. Song Ci was ordered to come to Tonggu and repeatedly stated to the people that sacrificing to the River God was nonsense, and promised to find out the truth. His arrival made the old county magistrate feel threatened. Under the instruction of the old county magistrate, his followers pretended to obey Song Ci and secretly oppressed him, trying to kill Song Ci without anyone knowing. When waves of dangers fell on Song Ci, children continued to disappear, which made the people lose trust in Song Ci and forced him to sacrifice to the River God quickly. Under pressure from many parties, Song Ci investigated carefully and used his superb forensic methods to make the corpse "speak". He gradually locked the real murderer and discovered the huge conspiracy behind it. In the end, Song Ci risked his life to bring the real murderer to justice.