In 1920s Shanghai, detectives Zhan Tianyuan and Liu Weiyi run a private agency while both loving childhood friend Rong Shaojuan. When Rong dies helping Zhan's case, their rift drives Liu to join the police. The connected disappearance of Xiang Jingrong brings her daughter Zhang Ziqing from abroad to the agency. Zhan and Zhang uncover crimes orchestrated by crime lord Mr. Bai, paralleling Liu's police investigation. Ultimately, they dismantle Bai's syndicate, resolve past misunderstandings, and find new beginnings.