Wolf(2004)

Original title: El Lobo

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.