A high school student, Young-Sin (Park So-Dam), gets hit by a car at night. Soon, she suffers from mysterious ailments. Priest Kim (Kim Yun-Seok) knows the Young-Sin and visits her in the hospital. He is sure she is possessed by demonic spirits. He prepares for an exorcism with the help of the Korean Catholic Church. Priest Kim requires a deacon to help him, but all the deacons flee after taking part in the exorcism. Seminary student Choi (Gang Dong-Won) is chosen as the 11th deacon to assist Priest Kim. They have only one day left to save Young-Sin with their lives all at stake.