A boy gets possessed by an evil spirit so called the ‘Guest’ that makes people go mad and kill their most close and loved ones. Even though he is an inherit of a shaman family, his grandfather calls an exorcist for help. However, during the ritual, the exorcist himself gets possessed by the evil spirit, and goes to kill his own parents and a female detective who was nearby. The evil spirit, who called himself the ‘Guest,’ then hides away somewhere. Two decades later, the boy becomes a shaman who drives a taxi for a living. After witnessing a possession of the ‘Guest’ one day, he decides to track down the Guest for revenge. Fate leads him to cross paths with an exorcist priest - a younger brother of the exorcist who got possessed, and a female detective - the daughter of the killed detective. They go around all mysterious cases related to evil spirits that happens around to find and destroy the Guest once and for all. However, the closer they get to the Guest, it dispatches stronger evil spirits to them, and hurts them and their surroundings. At one point they were sure that the Guest was inside Hwa-pyung’s father. The exorcism practice on his father resulted in his death, but the evil spirit inside him was not the Guest they were looking for. He is still somewhere out there, and they have to find him soon....