Zhu, an imperial inspector in Sichuan during an unspecified dynasty, suddenly receives a cryptic secret decree from the emperor. Taking four subordinates with him, Master He, Constable Du, clerk Wenming, and coroner Zhang, he heads north to Datong in Shanxi, where everything seems peaceful. Then, a murder takes place onstage during the Winter Solstice. Believed to be divine punishment, the case is investigated by Zhu, who eventually discovers that behind the stage accident lies a grave crisis that threatens the fate of the nation. Zhu and his men go on to solve the "Miss Gao's Suicide Case," the "Strange Fire in the Capital Case," and the "Assassination of the Cangpai Sect Leader Case." They all seem straightforward, with no need for deduction, but Zhu discovers that each conceals a deeper mystery.