A strong typhoon sweeps through Seoul. Han Ji-yoon receives a call from her fiance Park Do-hoon saying his home is flooded and asking to stay for a few days, and she agrees. However, the moment she prepares to open the door, a prophecy appears in the mirror—seven days later, a zombie disaster breaks out, and her fiance and younger sister will join forces to seize all her property and eventually tear her to pieces. Separated by only a single door, Han Ji-yoon engages in a life-and-death battle of wits with the two of them, trying her utmost to survive until the end amidst the doomsday catastrophe.