The protagonist Mengxi, as an immortal soul, encountered some troubles when performing his mission with his master, allowing a soul to escape. The chain reaction caused by this incident not only caused the master to be arrested and sent to the realm of souls, which is also feared by immortals, but also caused the protagonist to be transferred from the most glorious position in the Soul Bureau, and turned to the Supernatural Events Research Institute that specializes in investigating supernatural events in the world. The main purpose is to lurk in the crowd, arrest some wandering souls who escape privately, and fight against warlocks who specialize in making evil spirits. As for the escaped soul, because it is possessed in the body of a living person, it gives the possessed person various abilities. It gave the possessed person unprecedented satisfaction. However, as the plot develops, some originally recognized facts seem to be overturned. The protagonist secretly investigates the true situation of the master's arrest in the research institute, and the escaped soul will be slowly devoured by the spirit of the possessed person, leading to a tragic ending.