On a Christmas Eve, a lifeless body of teenage boy is found. The victim's revenge-driven twin brother checks himself into a juvie to hunt down the suspects.

Eighteen-year-old Ha-min suddenly begins to see the number "365" every time he eats his mother's homemade meal—and the number drops with each bite. Believing it to be a countdown to his mother's death, he distances himself from her and her cooking. Years later, still haunted by the number, Ha-min lives cautiously, preparing for the worst. Just as he begins to find peace with his girlfriend Ryeo-eun, an unexpected truth turns his world upside down.

This drama centres on a building that is on the verge of collapse after a sinkhole incident. As the danger grows, four young people connected to the building in different ways begin to uncover corruption.