Train to Busan 3 continues the gripping saga of survival in a world overrun by zombies, following the events of Train to Busan (2016) and Peninsula (2020). Set years after the collapse of society, the world has been ravaged by the undead, with only small pockets of survivors clinging to life. The few remaining humans live in scattered, fortified enclaves, constantly threatened by the ever-growing zombie hordes and the collapse of humanity itself.

In this third installment, a new protagonist emerges with a dark past and personal connection to the outbreak. He is tormented by the loss of his family and home and haunted by a sense of guilt. Desperate for redemption, he embarks on a dangerous mission after hearing about a rumored cure hidden in an abandoned research facility near Seoul, the heart of the zombie outbreak. To succeed, he must form an unlikely team of survivors, each with their own tragic stories, and traverse the desolate, zombie-infested city.

As they journey deeper into the wasteland, they face not only the undead but also rival factions of survivors who have become hardened and brutal in their struggle for resources. Trust becomes a rare commodity in this lawless world, where humans are often more dangerous than the zombies. The group must navigate these moral challenges, battling both the living and the dead, all while clinging to the faint hope that they can find a cure to stop the apocalypse.