Set in the near future, a high-rise apartment building has been newly constructed in the big city.
The apartment building has residents from diverse backgrounds, but a new infectious disease breaks out.
Because of the outbreak, the high-rise apartment is sealed off. The residents struggle to survive, while stricken with fear and distrust of others.
Yoon Sae-Bom (Han Hyo-Joo) is a member of aspecial police squad.
She is decisive, determined, and does not easily get rattled.
She is excited to move into her new apartment, but, as soon as moves there, she faces a criss.
Jung Yi-Hyun (Park Hyung–Sik) is a detective.
He is smart and honest. For a long time, he has held romantic feelings for Yoon Sae-Bom.
They graduated from the same high school.
Jung Yi-Hyun struggles to protect Yoon Sae-Bom and other people.
Han Tae-Seok (Jo Woo-Jin) is a lieutenant colonel and belongs to the health service command.
He holds a key on the infectious disease outbreak.