Constanza, princess of Spain, meets Pedro, her promised husband and future king of Portugal. Amidst political intrigue, Pedro falls in love with Inès, Constanza's aid. Inès returns hastily to Spain, repressing her own feelings, but Constanza dies suddenly. Pedro goes against his father's decision to marry a crowned girl, and reunites with his loved one. Three Portuguese nobles, acting in collusion with the king, persecute Inès in a palace, and kill her by the sword. The prince's faction is at the verge of war against their own king, but truce is reached at Oporto. Pedro sulks in agony until his father dies; then, he obtains the extradition of Inès' killers, and exacts terrific vengeance upon them, before crowning Inès as queen, posthumously.