Lee Dae-ho, portrayed by Kim Sang-kyung, is a devoted single father managing the magnificent 120-story Tower Sky in Yeouido-dong, Yeongdeungpo District, Seoul. Respected by his colleagues, he harbors deep feelings for the restaurant manager, Seo Yoon-hee, played by Son Ye-jin, dreaming of a future together.
As Christmas Eve approaches, the building's owner, Mr. Jo, plans a spectacular "White Christmas" party for the tenants and VIP guests, featuring helicopters glimmering with lights that will shower snow over the celebration. Dae-ho is initially set to enjoy a day at an amusement park with his daughter Ha-na, but obligations to the party force him to cancel those plans. Unfortunately, the building suffers from malfunctioning water sprinklers due to frozen pipes, yet Mr. Cha, the safety section head, prioritizes the party over these critical issues. This negligence becomes apparent when the cook, Young-cheol, who is infatuated with receptionist Min-jung, sneaks out to impress her, leading to a kitchen mishap.
Meanwhile, rookie fireman Lee Seon-woo, portrayed by Do Ji-han, has just joined the Yeouido Fire Station, where he quickly learns that many firefighters spend more time on breaks than on actual firefighting. In a humorous initiation, his teammates prank him by ringing the fire alarm while he is in the shower, leading to a memorable and embarrassing introduction to his new team.
Just as the festive atmosphere peaks, disaster strikes when strong winds cause one of the helicopters to crash into the building, igniting a series of catastrophic events. The resulting fire spreads rapidly as shards of glass rain down on partygoers, including Mr. Yoon and Mrs. Jung, who are left scrambling for safety. Chaos ensues when a security guard mistakenly allows a group to enter an elevator just before an explosion traps them inside, claiming their lives in a tragic turn of events.
Dae-ho desperately works to save Ha-na, Yoon-hee, and colleagues, while heroic firefighters Kang Young-ki, played by Sol Kyung-gu, and Seon-woo join the battle against the raging fire. They strive not only to rescue those trapped but also to contain the blaze that threatens to engulf the building. As they find refuge in a Chinese restaurant within the tower, the firefighters bravely confront the fire's source on the 63rd floor.
In a climactic moment of bravery, Young-ki ultimately sacrifices himself to save Seon-woo and many others, detonating explosives in a last-ditch effort to halt the inferno, leading to the building's collapse. Amid the chaos and destruction, the film concludes with a haunting silence as the flames fade to black, leaving a somber yet heroic legacy of those who fought to save others. The closing credits roll as the poignant instrumental score underscores the gravity of their sacrifices.
