In the late Qing and early Republic of China period, there is unrest, bandits and warlords wreaking havoc, and rampant crime. A series of murders breaks out in Jiuhe Town, a small county in the northwest of China, in which many died in strange and mysterious ways, as if they were harmed by evil forces. This causes panic in the town and puts everyone in danger. So, the county’s female constables, San Geng and Qi Xi, are ordered to conduct in-depth investigations. Surprisingly, red phosphorus powder, commonly known as Gumizi, is found on the corpses and at the scene of the murder. This powder is commonly used by magicians in the martial world as a prop. To seek clues, the two of them invite the Western magician Xin Shi Si, who is deeply hidden in the mountains, to assist in solving the case.