Knocked out cold during his first day on the job, prison officer Juan (Alberto Ammann) awakens to realize that his co-workers have abandoned him in the middle of an inmate uprising. To survive, Juan must pose as a prisoner and befriend the riot's leader, Malamadre (Luis Tosar). As the violence escalates and political fallout mounts, Juan must use all his cunning to stay alive in this masterfully suspenseful Spanish thriller.