The opera is set in 15th-century Castile.
The Countess de Soria (soprano) plans to marry General Salvaterra (tenor), who has won a decisive victory over the Moors. However, he has also captured the Moorish Prince Muza (bass) and has fallen in love with his betrothed, the Princess Zulma (soprano). Zulma responds to Salvaterra and offers him a sash. Muza insists that Salvaterra keeps a promise to him to release him and Zulma; when Zulma says that she will stay in Castile, Muza swears vengeance. Estrella, countess of Soria, has heard of the love of Salvaterra and the captive Moorish princess, but remains convinced that he will return her love.
In the woods outside the city Salvaterra is warned by the knight Sambrano of Muza's threats, and takes Zulma to Salvaterra's castle, but is ambushed by Muza and his men. Alone at the king's palace, Estrella is downcast, while preparations continue for a victory celebration. The king of Castile offers Salvaterra the hand of Estrella but Diego, Estrella's servant, notices that he is wearing a sash from Zulma; Estrella is distraught, but amid the confusion the king orders the celebration to continue. Muza approaches the king and announces that his bride has been stolen by Salvaterra, and draws his sword. Muza is slain and the king banishes Salvaterra.
At a spot by the sea peasants and sailors are at work; Salvaterra and Zulma nearby. Sambrano arrives and tells his master that Estrella and Diego are approaching. When Salvaterra goes to arrange an escape by sea, Estrella notices a veiled woman and orders that she be taken to a cliff to be killed. When Salvaterra returns and finds Estrella she orders her men to take him. As a storm begins Sambrano arrives and Estrella's men are disarmed and Zulma rescued. Although Estrella calls destruction down upon her enemies, Salvaterra and Zulma put out to sea on a ship, and in despair Estrella stabs herself.
