Because Zuo Qianhu knew that Pudu Cihang was a demon. According to the plot of the movie "A Chinese Ghost Story", Zuo Qianhu knew that Pudu Cihang was a demon, and Pudu Cihang was afraid that Zuo Qianhu would reveal his identity. "A Chinese Ghost Story" is a costume romance film produced by Tsui Hark and directed by Cheng Xiaodong, starring Leslie Cheung, Joey Wong, Wu Ma, etc. It was released in Hong Kong, China on July 18, 1987.