In 1920s Shanghai, private detectives Zhan Tianyuan and Liu Weiyi are torn apart after their shared love, Rong Shaojuan, dies during a case. Liu joins the police, while Zhan continues investigating. When socialite Xiang Jingrong disappears, her daughter Zhang Ziqing returns to seek help. As Zhan and Zhang uncover a web of crimes linked to crime lord Mr. Bai, their path converges with Liu’s official investigation.