Zhang Yao, a down-and-out young man who makes a living selling things at a street stall, is forced by Su Wanqing to inherit the Su family's medical hall because of a marriage contract made twenty years ago. Bearing a Daoist seal and possessing knowledge of traditional Chinese medicine and mystical arts, he specializes in treating rare and difficult illnesses. He and Su Wanqing go from bickering adversaries to partners as they take on Liu Xuan, expose Gu poison, and save cancer patients. Along the way, he becomes increasingly entangled in an old feud between his master, Chen Jiudeng, and Old Mo, embarking on an extraordinary journey into mystical Chinese medicine in the modern city.