The film takes place on a train traveling from Seoul to Busan, South Korea's second-largest city. The story revolves around Seok-woo (played by Gong Yoo), a recently divorced man who is traveling with his daughter Soo-an (played by Kim Su-an) to visit her mother. As the train departs, a strange and mysterious woman boards, who later turns out to be infected with a zombie-like virus.