On Christmas Eve, at the luxurious Tower Sky twin tower building in central Seoul, residents and staff members busy themselves with Christmas preparation. A small fire in the restaurant kitchen attracts the attention of Tower Sky staff member Lee Dae-Ho (Kim Sang Kyung), who notices a faulty water sprinkler system. Building owner Jo (Cha In-Pyo) disregards the warning and goes ahead with the evening's Christmas party.
Helicopters are hired to circle the building and spray the building with man made snow during the Christmas party. Residents gathered for the event are amazed by the spectacle. Their amazement soon turns into terror when a helicopter loses control and crashes into the building, setting off a chain off horrifying events that threatens the lives of all the residents.