All the apartments within the complex get infected, except Building 101. The phone lines and Internet get disconnected, and they are all on their own. Sae-bom and Yi-hyun struggle with the constant conflict between the renters and owners inside the building, including the people outside. Meanwhile, their food depletes, and they are left with only one option, to go outside.

An infected person enters Building 101, and once again, Building 101 is under the threat of infection. Lieutenant Colonel Han enters the apartment complex with news to tell, but Sae-bom and Yi-hyun find him suspicious. A person goes missing due to the intrusion, and those with similar interests and minds stay close together.