At the cafeteria entrance in deep autumn, the impoverished teenager Xiao Jie hands his only half of a white steamed bun to his ailing mother. Head teacher Wang Laoshi sees this, pulls out his life savings of twenty thousand yuan, and lets him continue his studies. Before passing away, Wang Laoshi entrusts his daughter Lin Wan to him. For this debt of gratitude and promise, Xiao Jie signs a five-year closed training agreement, growing into a pillar of talent through grueling hardships. Returning after five years, he finds his benefactor's wife and daughter being bullied by relatives. He steps forward, guarding them with wisdom and responsibility, punishing the wicked, and ultimately joining hands with Lin Wan to fulfill the delayed promise before his benefactor's grave.