In the near future of South Korea, where it became lawless due to an economic crisis, a new authoritarian government implements the "Permanent Exile Law" to easily control the country. According to this law, death row inmates are permanently exiled to a detention center, the Purgatory, built in abandoned nuclear power plants. With a degree of self-governance granted by the government, the Purgatory gradually reaches a point where it is beyond external control, leaving the government struggling to find a solution. Yu-seong, a police officer who became a death row inmate due to the revenge for his daughter and wife, is offered a deal by the Director of NIS. Now Yu-seong must eliminate the Purgatory Boss, the king of the center, in exchange for possible pardon.