Mystic Nine follows Zhang Qishan as he joins forces with Wu Laogou, alongside Huo Xiangu and the other members of the Mystic Nine, when turmoil returns to Changsha. The mysterious disappearance of Unit 401 uncovers a century-old secret. Faced with life-and-death choices, bound by brotherhood, responsibility to their sects, and devotion to their country, they risk everything to protect their home and overcome the crisis.

罹患脸盲症的傲娇郡王兼总捕头江心白（罗云熙 饰）秘密来到河蛮暗查“癸草案”时，意外结识了行事乖张、野蛮生长、并且每个月都变身的江湖游医颜南星（宋轶 饰）。二人不打不相识，为了各自身上隐藏的秘密，他们一起经历了“三结三离”的奇妙姻缘，最终携手扫除癸草之祸。