19-year-old Yoon Young lives alone with her mother and prepares for the civil service exam while working part-time. Regardless of good heart and sincere will, unexpected incidents turn Yoon Young from a victim to the killer, driving her to prison and being called inmate "2037" instead of "Yoon Young." In a hopeless situation her co-inmates in Cell No. 12 with their own stories offer a hand of hope to protect Yoon Young...