Ryu Seung-Ryong comes back as a fool for his daughter. Outsiders not allowed, in room number 7 of the prison where all kinds of criminals are gathered, comes Yong-goo, a father with the sense of a 6-year-old, and Ye-seung, his 7-year-old daughter. The mission of these criminals in room number 7 is to protect these two who can never stay apart for a single moment. Will they succeed?