In the fourth year of Yonghui, an accident occurred in the Lishan palace. Emperor Li Yan fell into the "soul-locking pool" connected to the ghost world. After comatose for three days, he woke up as half human and half ghost. During the day, he wandered around the Tang Dynasty and was respected by thousands of people. The admiring King Linyang is fighting step by step in the treacherous power struggle between the deposed king and Li Wu; at night, he transforms into the ghost king in charge of the ghost domain of Chang'an, hunting down evil spirits in the Netherworld Ghost City and the City of Wasted Death, and maintaining the order of the human and ghost worlds.
He has a double destiny and a deep hatred: behind his father's mysterious and violent death, there is a conspiracy of the "Xuanyin Sect" left in the late Sui Dynasty. The sect uses the souls of living people as a guide to break through the underground "Ghost Suppression Monument" in Chang'an, release the soul-locking Ghost Emperor who has been sealed for thousands of years, and subvert the balance between the human world and the ghost world. In order to find out the truth and avenge his father, Li Yan fought secretly with Wu Zetian's forces in the human court, and used dragon energy to practice "Yin and Yang Unity Technique" to strengthen his body. At the same time, he gathered Yin agents in the ghost world to fight against the four generals of the netherworld. Qian, Lin Waner, the descendant of the human medicine house, and Su Qingmei, a secret ally, help each other wholeheartedly, but they are also deeply involved in emotional entanglements because of the "different paths between humans and ghosts" - Su Qingmei died to protect him, Lin Waner accompanied him for a hundred years and entered reincarnation, and Nie Xiaoqian stayed with him in the underworld as a ghost king.
When the Xuanyin Sect awakened the Soul-locking Ghost Emperor by offering Zen in Mount Tai, the Ghost Suppression Monument was cracked, and evil spirits were running rampant. Li Yan embarked on the road to find the "Reincarnation Stone" in Fengdu. He understood the "Heavenly Reincarnation Technique" in the Hongmeng Realm, merged the power of human souls, ghosts and heavenly ways, and finally became the "human, ghost and heavenly envoy". He killed the ghost emperor, sealed the cracks, and established new laws for humans and ghosts, but he witnessed the change of generations because of his immortal body.
