The Immortal Promise.

Zhang Xiaomei, commander of the Beiyi division, seeks revenge against Crown Prince Li Ye for orchestrating his father's death. When Zhang captures Li Ye's top spy, Zhu Qingzhu, he sees a chance to expose the prince. However, Li Ye betrays Qingzhu, using her as a scapegoat to avoid punishment. Just as she faces execution, Zhang Xiaomei spares her life and brings her into his household. As they grow closer, they fall in love, only for Li Ye to reemerge, determined to reclaim Qingzhu and prevent her from finding happiness with another man.