When a high-ranking North Korean defector is murdered abroad, South Korea triggers a security alert for defectors. Inspector Kim, responsible for protecting defectors, is anxious about not being able to find the young defector Ryu Soo-hyun, who has been out of contact for a month. Ryu Soo-hyun, who works part-time at a library, recently received a death threat letter and is now on the run. Every moment is filled with fear and terror, and he lost his stable life long ago. Today, on the day of the library's temporary closure, strangers visit the place, unlike usual. With different faces and stories, they approach Ryu Soo-hyun in various forms. Facing four different visitors under the threat of death, Ryu Soo-hyun is forced to welcome them and begin another day in the terror of death...