The protagonist Song Sheng, after death, came to the underworld to become the messenger of the underworld. Niu Tou and his partner Ma Mian Chen Xiaoqing were responsible for guiding the souls of the underworld, and were later involved in a series of conspiracies intended to overthrow the rule of the underworld. The old tribe of Beiyin, which once launched a rebellion, has been secretly watching the movements of the underworld, waiting for an opportunity to make a comeback. However, they did not expect that humans have also developed technology that is enough to fight the ghosts of the underworld and are preparing to occupy the underworld.
