Chen Ping'an is a four-year-old boy in the wealthy Chen family of Sheng'an County who possesses the memories of a previous life. He recognizes his father, Chen Yan, as a historical figure known as a treacherous minister who will eventually lead his family to ruin and execution. The Chen family is divided into Northern and Southern branches, with the Southern branch, despite its wealth, lacking political influence. The family places immense pressure on Chen Yan to pass the imperial examinations to secure their future. Upon realizing the catastrophic fate awaiting his family, Ping'an resolves to change their destiny by preventing his father from becoming an official.
Ping'an's first major action occurs when he discovers an invitation to his own hundred-day celebration under the name Chen Pingrui. He learns from his grandfather that his name was changed from Pingrui to Ping'an due to a fortune teller's superstitious advice, a decision made out of concern for his health rather than political ambition. Understanding the precarious position of the Southern Chen family, Ping'an decides he must sabotage his father's academic career. He devises a plan to make Chen Yan fail the upcoming Ke Examination, believing that if his father does not become a scholar-official, the family will not rise to power and thus will not fall to treason.
The plan is set in motion when Ping'an steals his father's Examination Pass, hiding it in the kitchen firewood pile. The household descends into chaos as the family searches desperately for the missing document. The pass is eventually recovered just before the exam, but the incident causes significant tension. Chen Yan, initially distant and absorbed in his studies, is forced to confront the situation. His wife, Lin Yuebai, is furious and blames Chen Yan for neglecting their son's education. In an attempt to resolve the marital dispute and force Chen Yan to take responsibility, Lin Yuebai sends Ping'an to live with his father in the front courtyard study.
Living with Chen Yan proves to be a difficult adjustment for both. Chen Yan, though a brilliant scholar, is inexperienced in childcare. He struggles with mundane tasks like dressing Ping'an and managing his daily needs. However, the forced proximity begins to thaw their relationship. Chen Yan starts to engage with his son, teaching him calligraphy and explaining social customs. He also seeks advice from Magistrate Sun, a local official and father of eight, who suggests that children's mischievous behavior often passes with time and should not be overly punished.
Despite the growing bond between father and son, Ping'an remains focused on his mission. He continues to look for opportunities to hinder his father's academic progress. The family dynamics shift as Chen Yan becomes more involved in Ping'an's life, balancing his studies with parenting. Lin Yuebai returns home, and the family appears to reconcile, though the underlying threat of the future remains. Ping'an is aware that the Ke Examination has been missed, but a make-up exam, the Luyi, is scheduled for the second day of the seventh month. He must find a new way to prevent his father from succeeding in this second chance, all while navigating the complex social and political landscape of the Chen family and Sheng'an County.
