In the thirteenth year of Yongle, strange things happened frequently in Qingxi County in the south of the Yangtze River. Three people died unexpectedly one after another. Their deaths were strange and they all had crescent-shaped marks on their bodies. The government had been investigating the case for many days without any clues, and the people called them "evils." Jin Yiwei Shen Yan, who has a vicious tongue and is "socially fearful", was "assigned" by his superiors because he did not want to be involved in the internal affairs of the capital. He came here to investigate the case, but unexpectedly met Su Qingci, a widower who was disguised as a man and had great skills. One relied on logical reasoning to grasp the details, and the other relied on autopsy skills to solve doubts. The two went from the mutual hostility of "Can you do it, little dog?" To the tacit understanding of "I accept this operation", and tracked down the secrets behind the serial murders. But as the clues deepen, Su Qingci's identity as a woman disguised as a man may be exposed at any time. Shen Yan also discovers that the case is actually related to an old case many years ago. Not only do the two have to battle wits with the murderer, but they also have to deal with the open guns and secret arrows around them. In this Ming Dynasty version of the "detective partner" adventure, can the truth be found out?
