"You’re its prey the moment you touch it." One day, a terrible virus variant attacks Seoul! Yeon-woo is on a school trip to Seoul, and is excited thinking that he can finally get along with his one classmate, So-yeon, whom he has a crush on. However, during this time, unidentified cells appeared in front of Yeon-woo’s class, who were sightseeing in Seoul. The mutant cells manifestation quickly turns Yeon-woo and his classmates’ school trip into hell as anyone who comes into contact with the cells will become a hideous monster that wants to consume anything with flesh...! Will Yeon-woo be able to leave Seoul safely?