Raised with care since childhood by nine masters in Kunlun, Li Mucheng carries a marriage contract down the mountain upon reaching adulthood to fulfill it, repeatedly meeting cold receptions at the Lin family. Sensing the Lin family is infested by evil spirits, he steps in with superior medical skills to save the critically ill Elder Lin, thereby uncovering his life background—he is the surviving descendant of the once-prominent Li family of the capital. Faced with wealthy family disputes and secret schemes, Li Mucheng stands firm with a benevolent heart, resolves crises one after another with his abilities, and ferrets out treacherous villains. He is determined to clear his family's grievances, revitalize the family lineage, and make an agreement in the Lin family ancestral hall to use three months to prove himself and uprightly marry Lin Manqing.