Gu Jin, Yin, and Hong Yi come to the Mortal Realm to look for the Stone of Lives. Yan Shuang, who can't find anything in the Wuji Cave, joins them. In order to repay them for helping her before, she uses her eagle eyes and locates the Stone of Lives, which unexpectedly is under the control of a sea serpent. A scheme unfolds as Yin disguises herself as a bride to get close to the creature while Gu Jin protects her in secret. Yan Shuang and Hong Yi, both skilled in formations, reluctantly partner up to infiltrate the sea serpent's lair and set up an ambush, waiting for the right moment to kill it.