Jae-yoon, a late military enlistee, and his girlfriend, Young-joo, break up over the phone over growing misunderstandings. But a zombie outbreak rocks the world. A national emergency is declared, a plane crashes in the city center, and Jae-yoon and his unit get trapped on top of a Seoul skyscraper. Young-joo risks the zombie-filled streets to find him. Can their love survive the apocalypse?
After downing the supply helicopter, First Sergeant Jung Tae-hwa realizes that survival at their station is impossible. He plans to lead his platoon in an escape from the zombie-ridden A Tower. Meanwhile, Young-joo's group finally reaches the gate of A Tower, only to be greeted by a horde of zombies.