When Gu Family Head Gu Xingzhi is holding the capping ceremony for his adoptive son Gu Jingheng, he unexpectedly encounters the beggar A Qing with a crescent moon birthmark on his forehead, which arouses his suspicions about the birth of his son back then. Secretly investigating, he discovers that the dowry wet nurse Sun Shi, in order to let her own grandson enjoy boundless glory and wealth, secretly swapped the infants, and repeatedly designed plots to frame A Qing with the intent to poison the master's family. Gu Xingzhi plays along to catch them in the act, producing evidence and the ancestral Guimai Jade at the longevity banquet to expose the truth of the son-swapping in public, punishing Sun Shi and Gu Jingheng. In the end, A Qing acknowledges his ancestors and returns to his clan, bestowed the name Gu Zhihuan, and inherits the hundred-year foundation of the Gu family with a pure and kind nature.