Set in the early years of the Republic of China in Tianjin, a series of mysterious deaths among dozens of sewer workers leaves the people in a state of panic. The discovery of shattered bodies floating in the river leads fortune tellers to claim that water demons are at large, bringing great calamity to the city. Gu Zhiyuan, a laid-off police officer, struggles to make ends meet by taking odd jobs at the docks to support himself and his daughter Ling Long. One day, a ferocious river creature emerges onto the shore, wreaking havoc on homes and lives, and abducts Gu Zhiyuans daughter Ling Long. Determined to rescue his daughter, Gu Zhiyuan teams up with Tang Xiaowei, his estranged sister-in-law with whom he had a distant relationship. Together, they embark on a journey of redemption, exploring life, family, and self-discovery in their quest to save their loved ones.