An apocalyptic thriller set in a time when infectious diseases have become the norm. The drama shows class discrimination, subtle psychological wars and a fierce struggle for survival taking place in a multi-storey residential complex isolated from the outside world due to a new type of infectious disease.
Yoon Se Beom is an agent of the special police squad. She is determined, so she makes decisions quickly and implements them without hesitation. But as soon as she fulfills her dream of moving to a new apartment, she will face an unprecedented crisis.
Jung Yi Hyun is a smart and honest detective from the Violent Crimes department, working for the benefit of society, not for personal gain. He has always been in love with his classmate friend Yoon Se Beom. Jung Yi Hyun gets caught up in the maelstrom of events after accepting an unexpected offer from Yoon Se Beom.
Han Tae-seok is the head of the medical unit of the armed forces. He is the one who holds the «key» to a new infectious disease. He was instructed to determine the cause of a new infectious disease and prevent its spread. Han Tae Seok is a character who transforms instantly, so it's hard to «read» him.