During the Republic of China period, a series of shocking events occurred in Qian'an Town, located in the southeast. Within a month, five people inexplicably committed suicide, causing great alarm among the townspeople. The town's night watchman not only had the responsibility to announce the time but also carried the heavy burden of exorcising demons, thus requiring someone with exceptional skills to take on the role. The Xu family in Qian'an Town had a high reputation, and the patriarch, Xu Datong, was at a loss regarding the suicides. Ever since the previous night watchman mysteriously froze to death in the midst of a fire in June, no one dared to take the position until a foolish outsider named Mao Xiaoshan accepted the job. Mao Xiaoshan claimed to have studied the Taoist arts of Maoshan, and after arriving in Qian'an Town, he patrolled the streets every night. However, just as the town was beginning to stabilize, a rich merchant was brutally murdered in his home, causing extreme panic among the residents. Following Xu Datong's suggestion, they raised funds to invite an outside master to perform rituals to drive away evil spirits. However, after the master performed his magic, he identified the person possessed by the evil spirit to be Mao Xiaoshan's childhood sweetheart, Wen Yingying. Mao Xiaoshan's real name is Xu Song, and he is Xu Datong's nephew. Many years ago, after being framed by his uncle, resulting in his family being destroyed, he adopted a new identity and devoted himself to learning skills. Now, returning to Qian'an Town under a new identity, his true purpose was to investigate the evidence of Xu Datong's long-standing collusion with neighbors and betrayal of kin, seeking vengeance for his parents. To save Wen Yingying, Mao Xiaoshan had to expose the true face of the master, who was deceiving people with illusions, but in doing so, he also drew Xu Datong's suspicion. Under numerous tests by Xu Datong, Mao Xiaoshan walked on thin ice, and a single misstep could cost him his life. After overcoming many obstacles, Mao Xiaoshan finally used his identity as the night watchman to uncover Xu Datong's conspiracy to poison the town's water supply using an ancient formula from the Xu family. It turned out that Xu Datong had harmed his brother years ago just to obtain the century-old secret recipe, which had miraculous effects in saving lives. However, after Xu Datong's modifications, the formula could also cause hallucinations, leading to madness, which was the source of the recent bizarre occurrences in Qian'an Town. With Wen Yingying's help, Mao Xiaoshan exposed Xu Datong and his son’s conspiracy, dispelling the dark cloud that loomed over the townspeople's hearts and restoring his parents' honor, ultimately bringing back a sense of peace to his homeland.