[2][3] The film is about a developmentally disabled man wrongfully imprisoned for murder, who builds friendships with the hardened criminals in his cell, who in return help him see his daughter again by smuggling her into the prison.

The movie is based on the real-life story of a man who was tortured and pleaded guilty under duress to the rape and murder of a 9-year-old girl on September 27, 1972 in Chuncheon before being finally exonerated in November 2008.

Back in 1997, 6-year-old Ye-sung and her father, Yong-gu (who has a developmental disability), stare into a store window admiring a Sailor Moon backpack.

Yong-gu is sent to prison, where he shares a jail cell (titled "Room 7") with five other inmates, all of who initially dislike him for his falsely accused crime and his disability.

In court 16 years later (in the present), Ye-sung, the prison warden and the Room 7 inmates all attend Yong-gu's trial to prove his innocence.

The judge exonerates Yong-gu by overturning the previous verdict and granting him a posthumous acquittal, as well as a court order to re-investigate the girl's death, to the joy of the former Room 7 inmates, the warden, and tearful Ye-sung while the police commissioner can only sit silently in defeat.

The scene then returns to the beginning of the film, where Ye-sung has a vision of Yong-gu and her younger self on the hot air balloon waving goodbye.

[10][11][12] 32 days after its release, it became only the eighth film in Korean cinema history to break the 10 million mark in ticket sales.

[18][19] On March 15, 2013, 52 days after its release, ticket sales reached 12.32 million, making it the seventh highest grossing Korean film of all time.

[26] Kross Pictures to produce the official Hindi remake of the movie in collaboration with Indian Film Studios and was directed by Umesh Shukla.