Shi Jinhua, the daughter of a butcher, marries into the Marquis of Dingbei's household at eighteen and becomes the stepmother of three unruly young masters. The entire capital waits to see her make a fool of herself. On her wedding night, her stepson locks the door and sets a dog on her. She stabs the mastiff to death with a single blow and chops down the door with her knife, terrifying the young troublemakers. From then on, she stands up for her timid third stepson and exposes servants who bully their masters. She also helps her second stepson collect debts. Impressed by her ability, the old madam entrusts her with all the household account books. But when she investigates, she uncovers missing funds, secret arms smuggling, and the poisoning of the previous marchioness, with the trail leading straight to the Grand Princess. When the eldest son is framed and imprisoned, Jinhua uses her connections among ordinary people to expose the forged evidence and confront the truth before the emperor, bringing down the Grand Princess in one decisive move.