Su Wanqing, the daughter of the wealthiest merchant in Jiangnan, to protect her family property, mistakenly enters a teahouse in the rain and mistakes Lu Yuan, the Prince of Zhenbei investigating cases in disguise, for a matrilocal son-in-law, forcefully bringing him back. Lu Yuan plays along to enter the family and investigate cases, and the two join hands to expose corruption and quell family disputes. After entering the capital, she resolves the Empress Dowager's difficulties with her business acumen and is titled the legitimate princess consort. With war in the northern border, she manages logistics, personally goes to the front lines to stabilize the troops' morale, and shatters the treasonous conspiracy. Finally, overcoming all opinions, she proposes border mutual markets to stop war with commerce, winning peace for the world.