With the help of Mergen, Hongjun and Li Jinglong have successfully roused the ghost king from his waking dream - but the danger is not yet over. The group soon learns that the one responsible for entrapping the ghost king is none other than the white deer Mergen seeks, a god of dreams who has fallen under the sway of the mysterious yao king. Worse still, the yao king has used the deer's power to take control of the ghost king's army, and more undead soldiers are on the way.

Before they can formulate a plan, Lu Xu, the fleet-footed scout Mergen rescued on the northern border, sets off alone in the snow. When Hongjun goes after him, he too finds himself snared in a nightmare of the enemy's making-a vision of his own forgotten past that will upend everything he thought he knew about himself, his parents, and even Li Jinglong.