Oh Soo Min (Yun Woo Jin) is a dutiful young Catholic priest, filled with energy. He is a member 643 Regia. The group performs exorcisms unofficially. In the past, his own mother was possessed by a devil. She could not receive an exorcism and she consequently died. After that, Oh Soo Min was taught by Priest Moon Ki Sun (Park Yong Woo) (whose formed 643 Regia) on how to perform exorcisms. Meanwhile, Ham Eun Ho (Jung Yoo Mi) became a doctor after her family went through an unfortunate accident. She wants to save people's life. Now, Ham Eun Ho works in the emergency room of a hospital. she does not believe in God, but she witnesses a supernatural phenomenon and meets Priest Oh Soo Min. Ham Eun Ho faces a big change in her life.