Based on a true story. In the 70s, during the last stages of Franco's dictatorship, Txema, a basque construction worker, is arrested because of his connection to some terrorists who have just committed a murder. The secret service see in him an ideal candidate to infiltrate the terrorist band ETA and become a mole, so they try to offer him a deal if he will do so.
A tale of cheats and impostors, taking its inspiration from true facts and from one of the most intriguing characters of recent decades: the spy Francisco Paesa.
Two journalists investigate the criminal activities of the GAL (Grupos Antiterroristas de Liberación), a secret terrorist organization founded in the eighties and financed by leading figures in the Spanish government and security forces to hunt down and exterminate both members and collaborators of the terrorist gang ETA.