A man promises his mother to come back a greater person. Until now, he's been a condemned criminal with false hopes and dreams. Only after his life tanked did he realize how miserable he made his mother even though she neither resents or hates him.
Seok Woo, his estranged daughter Soo An, and other passengers become trapped on a KTX train (high-speed train) heading from Seoul to Busan during a disastrous virus outbreak in South Korea.