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?
In the midst of the zombie crisis, Jae-yoon and Young-joo reminisce about their happy past and long for each other even more. Meanwhile, Jae-yoon and his squad mourn the loss of their comrades but find relief in the news of a supply helicopter's arrival. Young-joo’s group encounters Tripeater, who has been bitten by a zombie but has not yet turned.