The legitimate elder sister looks down on the lame blacksmith, forcing Xu Nanxing to take her place in the marriage. Everyone thinks she is marrying into a poor blacksmith's shop and can only suffer for the rest of her life. Who would have thought that a useless copper button would actually expose the fake medicine conspiracy behind her mother's disappearance? Her husband Lu Chen is silent and reliable, protecting her safe and sound, but the Xu family and the chamber of commerce push step by step, wanting to make her shut up and accept her fate. She refuses to accept it! With a gold abacus, she settles high-interest loans, exposes fake accounts, joins hands with her blacksmith husband to investigate the Xu family back, and uncovers the dark secrets of the chamber of commerce. When everyone is waiting to watch her make a fool of herself, Xu Nanxing sneers coldly, "Since I have taken over this account, I will definitely settle it to the end!"