Based on the true story of an infiltrator in the ETA terrorist group whose mission, in the early 1960's, brought down a quarter of its members, including the upper echelons of the organization. Lobo is the story of a man used and betrayed by Franco's secret services, rejected by his own family and declared a priority target by ETA. Lobo, however, knew how to save himself by his own means and persevered with his mission. At the end of the operation, Lobo was forced to change his identity and face, and disappeared without a trace. Yet he left an impression so deep that, even today, terrorist cells departing for Spain to perpetrate their attacks receive a spare bullet with Lobo's name on it.