Hyeon-seok, a former taekwondo champion, has recently moved to Seoul for work at a small online streaming firm in a Gangnam office building. His martial arts skills are put to good use when a mysterious man covered in blood appears in the building and starts attacking people, who swiftly turn into flesh-craving zombies and bite any human being they encounter, rapidly spreading the infection. The owner of the building orders the exits to be locked, sealing everyone inside. Unable to call for help because the phone lines are dead, Hyeon-seok and his co-worker and secret crush Min-jeong try frantically to find their way out ...
