On the wedding day of the legitimate daughter of a military general family, Shen Nanxing, the groom Gu Yunting disregarded propriety for personal reasons and ignored the imperial decree of marriage. She resolutely tore up the marriage letter to divorce her husband in public, and joined forces with her sworn brother Xiao Yan. Following clues, the two thoroughly investigated the corruption case of border military provisions, outwitted the treacherous officials in the imperial court, and purged the corrupt elements in the army. With her extraordinary wisdom and bravery, she was conferred the title of Lady Protecting the Country, and she also came to know, protect, and stay with the Prince Regent Xiao Yan, who hid his identity, guarding the rivers and mountains through the years together and going to the prosperous fireworks side by side.