During the Song Dynasty, Song Ci came to Changting County to take up a post and devoted himself to studying the method of autopsy in order to write a book, "Xiyuan Jilu". Suddenly one night, a man and a woman died at the same time, shocking the whole county. Song Ci immediately intervened in the investigation after learning about it. After the investigation and autopsy, Song Ci found that something was wrong. This was not a simple murder case. When he was at a loss, Song Ci thought of Danqing, a woman he had not dared to see for three years. It can be said that there was nothing in Changting County that Danqing didn't know. So Song Ci went to Danqing's relatives to ask about the two recent murders and asked Danqing to investigate the case together. After a series of analysis, reasoning and visits, the truth finally came to light.