One day, Joon Woo wakes up to find that a mysterious virus outbreak has occurred. The outbreak suddenly spread throughout Seoul and rapidly grows out of control, trapping survivors alone inside their apartments without access to cellular data, Wi-Fi, texting, or phone calls. Joon Woo and Yoo Bin struggle to survive in an isolated apartment complex from those infected with the virus. (Source: Soompi) ~~ Based on the original scenario of "Alone" by Matt Naylor.