The film takes place on a train traveling from Seoul to Busan, South Korea's second-largest city. The story follows a group of passengers, including a young couple, Seok-woo (Gong Yoo) and Soo-an (Ma Dong-seok), who are on their way to visit Soo-an's mother. As the train departs, the passengers settle in for a relaxing journey. However, their tranquility is short-lived, as a zombie outbreak suddenly occurs on the train.