Mendo, the King's ambassador, is captured by a group of outlaws. Spared his life by the leader, Lope, Mendo offers to obtain Lope's pardon and effects a reconciliation between Lope and his father. A love rivalry and tensions with his father lead to Lope fleeing: Mendo, now Chief Justice to the King, arrests him. In the accumulating darkness of the final act the central characters ponder on their individual contributions to Lope's death.