Daniel Monzon writes and directs this suspenseful Spanish prison thriller based on a novel by Francisco Perez Gandul. Alberto Ammann stars as trainee prison guard Juan Olivier, who is injured when a prison riot breaks out as he is taking his induction tour of the prison. The uprising, initiated by the charismatic and dangerous Malamadre (Luis Tosar), is a politically-motivated rebellion intended to force negotiations with the authorities over prisoners' rights, and to this end Malamadre takes three Basque terrorists hostage. Caught amidst the ensuing chaos and desperate to protect himself, Juan pretends to be an inmate and ends up becoming Malamadre's right hand man.