The train from Seoul has arrived in Busan. On the way to the train station, southeastern South Korea and the southern terminus of the Gyeongbu Line. The train accidentally hit a deer that was passing by, the deer died. The train driver didn't care whether the deer died or not, he continued driving the train.

The deer that was hit and killed came back to life and attacked a man who was crossing the train tracks. The man turned into a zombie and the zombie virus spread widely to parts of the city of Busan.

In the train. You, your parents and other passengers were shocked because the back carriage was very noisy, apparently the virus had reached the train you were on and the passengers in the back carriage were infected. All the passengers, you and your parents ran for your lives, not caring that the train was still running.

The train finally stopped at the station. Passengers ran for their lives, you were separated from your parents. There is a male zombie running towards you, you run to save yourself from this terrible zombie outbreak. The zombie outbreak has spread throughout the city where you live.

After a long time running for safety. You arrive in the forest behind the city which is not affected by the virus outbreak. At the entrance, there were many soldiers with long-barreled rifles in their hands and a fence surrounding the entrance. They are starting to be alert because they suspect you are a zombie. You raise your hands indicating that you are human, not a zombie.

Commander named Dong-hyun opened the gate and took the frightened you inside.