Don Plutarco, his son Genaro and his grandson Lucio live a double life: on one hand, they are musicians and humble farmers; on the other, they support the Campesina peasant guerilla movement's armed efforts against the oppressive government. When the military seizes the village, the rebels flee to the sierra hills, forced to leave behind their stock of ammunition. While the guerillas organize a counter-attack, old Plutarco executes his own plan. He plays up his appearance as a harmless violin player in order to get into the village and recover the ammunition hidden his corn field. His violin playing charms the army captain who orders Plutarco to come back daily. Arms and music play a tenuous game of cat-and-mouse which ultimately results in painful betrayal.