A 19-year-old girl named Yoon-Young, who lives alone with her deaf mother, prepares for a civil service exam while doing a part-time job and becomes a murderer after an unexpected accident. Yoon Young is imprisoned in a prison and is called her prisoner number 2037 instead of her own name. In this desperate situation, her fellow prison mates in Cell room 12, each with their own story, reach out to protect Yoon-young.