In Seoul, there is one man named Seok-Woo who is a busy fund manager or can say he is a workaholic divorced father. He barely has time for his daughter. He was also selfish and neglects her daughter Su-an. On her daughter's birthday, he was going to work but, her mother insisted to be with his daughter. Su-an wants to spend her birthday with her mother who lives in Busan.
After this, he thought to fulfill his daughter's wish, and they left for station to en route Busan. On the train, other passengers were also going to their respective places. Some were working-class people, one was a baseball team, elder sisters, and homeless beggar.
As the train starts, one infected woman enter into the train. She doesn’t have a ticket neither anyone was aware that she boarded the train, and she is infected too. She then becomes a Zombie because of the infection, later started attacking the passengers. Afterward, the infection was spreading promptly all over the train. Those who were affected by the virus were becoming Zombies, attacking other people.
At one station, the train got stopped, those who were normal were shifting to another train, and in different cars. There was a group of a football team, one working-class man with his pregnant wife, Seok-Woo with his daughter, and the homeless beggar. Though, soon Zombies arrived on that train. At last, Seok-Woo and his daughter isolated themselves with a pregnant woman in the front car of a train. Will they survive from the infected people? The rest of the story is based on that only!