The film is an investigative documentary that starts with the accidental discovery of a poem written on the ruins of a building near the railway sometime in the childhood of the director, Alberto Pascual. In the swampy area of the Sierra de Madrid, we discover the history of one of the darkest episodes in the history of Spain during the Franco dictatorship, the sentence of forced labor, a legal instrument that allowed state and private companies to use political opponents of the regime as labor.