![Happiness](https://image.chilimovie.com/region2/en/300px/20230823/j3Q4Vamcb0p7uoXMkkvIp36oMJe.jpg)
Sae Bom learns that happiness is not your house but the person you are beside. And that person to her is Yi Hyun. She determines to make it back to the apartment, her house, and to where Yi Hyun would be. Dying or getting infected doesn't scare her as she tells him to wait for her.
Kim Se Hoon, the guy on the 15th floor, goes missing. Sae Bom and Yi Hyun try to figure out why he disappeared and what he was trying to hide. The residents in the building flock to his unit and squabble over the supplies he had stashed. Meanwhile, Yi Hyun contends with his thirst and keeps Sae Bom from knowing about his infection.
A new type of deadly virus spread throughout the city, and the apartment where has different social classes of people is sealed off. With the fear of the virus, and the conflicts of the different classes, the residents have to spend and survive in the new habitation.