On Christmas Eve in 2012, in TowerSky, a 120-story skyscraper in downtown Seoul, South Korea, there is Yunxi (Son Ye-jin), a strong Chinese restaurant manager, Li Taihao (Kim Sang-kyung), a reserved building property captain and single father, a domineering and arrogant lady, a chairman who is superior to others, and a careless little chef who loses things... People of different professions and identities are moving along their own tracks. They are either intertwined with each other or have nothing to do with each other, but they don’t know that a disaster is about to befall them. As night falls, just as people are immersed in the romantic and happy atmosphere created by artificial snowfall, an accident suddenly occurs. A helicopter dedicated to snowmaking loses control and crashes into the building due to the strong airflow, causing chaos and an uncontrollable fire. Just as it was as beautiful as heaven, the luxurious and beautiful building instantly turned into a cruel purgatory on earth...