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.

被封在山中五百年的庚辰仙府师祖司马焦（陈飞宇 饰）与意外来到修仙界的廖停雁（王影璐 饰）相遇后，被其无欲无求的“咸鱼”本能降服，从此廖停雁开始引导司马焦步步向善，成为了改变他的人，过程中他们萌生情愫，在仙府、魔域和人间经历了一段跨越三世的爱恨纠葛，最终两人选择守护爱人，维护三界太平。
该剧改编自扶华的小说《向师祖献上咸鱼》。