The events in the opera take place at the beginning of the fifteenth century in Spain, with the background of a revolt against the King of Aragon by Count Urgel of Biscay In command of the King's army at Saragossa is the Count of Luna. Years before, when the Count was a young child, a gipsy woman was discovered near the cradle of his brother, Garcia. Terrified servants chased the old woman away, but the boy gradually grew ill. His father searched for the gipsy, accusing her of witchcraft, and had her burned at the stake. The woman's daughter kidnapped Garcia in revenge, intending to throw him into the flames of her mother's pyre. In her frenzy, however, she threw her own baby into the fire and has brought up Garcia as her son.
ACT I - THE DUEL
Scene 1 - Aliaferia palace in Aragon
Ferrando, Captain of the Guard, stands watch with other retainers and soldiers, before the palace while Count of Luna maintains his nightly vigil beneath the windows of Leonora, with whom he is in love. Upon his companions' request Ferrando relates how, as an infant, the Count's brother was bewitched by a gipsy, then suddenly vanished. A child, presumably the same one, was later found dead amid the ashes on the site where the old woman had been burned at the stake in punishment for her crime. The perpetrator of the gipsy's vengeance, he tells them, was her daughter, an evil woman of whom nothing has been heard since. As a clock strikes midnight the soldiers and retainers disperse.
Scene 2 - The gardens of the palace
Leonora, a lady-in-waiting to the Princess of Aragon, tells her attendant Ines of the first stirrings of her love. She met a mysterious knight at the tournament but then, with the outbreak of civil war, she did not see him again. Lately, however, he reappeared to serenade her as a troubadour. Ines tries to persuade her lady to forget the stranger, but Leonora affirms that she would gladly die for him. As they retire to their rooms, the Count appears, determined to declare his love for Leonora. His soliloquy is interrupted by the troubadour's song. Leonora rushes out to greet her love, but in the darkness mistakenly approaches the Count. At this moment the troubadour appears and Leonora realizes her error. The Count's jealousy and anger grow vehement when the troubadour reveals himself as Manrico, an officer in the army of Prince Urgel and thus the Count's enemy in the civil war. As the Count and Manrico rush off to settle their dispute in combat, Leonora falls unconscious to the ground.
ACT II - THE GIPSY
Scene 1 - A gipsy camp in Biscay
Several weeks have passed. In a cleft in the mountains of Biscay a company of gipsies greet the dawn with a joyous chorus, to which they beat time with their hammers. In their midst, by a bonfire, sits the old gipsy woman Azucena and by her side Manrico. She is gazing into the fire singing a song full of weird, terrifying images, savage flames, an exulting crowd, a poor old woman dragged and beaten by soldiers, and a ghost that cries `Avenge me!'. The gipsies disperse to the villages to earn their daily living. Manrico remains behind and asks to know the meaning of Azucena's song. She tells how she saw her mother dragged to the stake, while she followed behind carrying her infant son on her back. She called to her in vain to give her a mother's blessing but the soldiers pushed her away roughly Her mother was thrust into the flames; and from the billowing smoke her ghost seemed to cry out to her daughter for vengeance. Accordingly Azucena had gone to the Count of Luna's palace, stolen the Count's eldest son intending to cast him on the pyre. His piteous sobs moved her; and she wavered. Then in a delirium she saw her mother's ghost. Terrified she threw the child on he embers; the mist cleared from her mind and, there was the Count's son by her side. It was her own baby that she had murdered. Manrico is horrified; he has always imagined her to be his mother and now? Azucena hastily reassures him. Of course she is his mother; when she had found him half dead on the battlefield of Yelila had she not nursed him back to health? Manrico recalls with pride how he stood alone against the hated Count of Luna; yet earlier in a duel when he had the Count at his mercy and he could have killed him some instinct had held him back. A messenger appears with dispatches from the Count of Urgel. He has captured the fort of Castellor, and wishes Manrico to take charge of the garrison. Leonora thinking him dead has decided to take the veil. Manrico, ignoring Azucena's frantic attempts to detain him, hurries away.
Scene 2 - A covent near Castellor
It is night and the Count and his men are lying in wait at the convent where Leonora is due to arrive. When she appears with Ines the Count rushes out and seizes her, but Manrico appears and stops him. His men hold back the Count's forces while Manrico leads Leonora away to safety.
ACT III - THE GIPSY'S SON
Scene 1 - Count of Luna's camp
Soldiers under the Count's command prepare to besiege Castellor while di Luna thinks of Leonora in the arms of his enemy. Ferrando reports that a gipsy woman has been taken prisoner in the vicinity of the camp. Azucena is brought in and explains that she is searching for her son. When she learns that her interrogator is Count of Luna, fear betrays her identity and confirms his suspicions that she was responsible for the abduction of his infant brother. Led to believe that she is Manrico's mother by Azucena herself, di Luna decides to use the gipsy as a pawn in his plan to avenge his brother and reclaim Leonora.
Scene 2 - Inside Castellor
Manrico and Leonora prepare to be married, but she is uneasy with thoughts of the attack on Castellor, which is to come at dawn. Manrico reassures her, telling her that love will strengthen him in the face of death at his enemy's sword. As they are about to approach the altar Ruiz, one of Manrico's soldiers rushes on with the news that Azucena has been sentenced to death at the stake. Manrico resolves to save her and orders his men to prepare for battle.
ACT IV - THE ORDEAL
Scene 1 - The Ramparts of Aliaferia Palace
Manrico's gallant attempt at rescue has failed; both he and Azucena are now imprisoned in a high tower in the palace of Aliaferia. From the garden below Leonora listens to the distant chanting of the monks, with their prayers for the souls of those about to die, and the voice of the troubadour proclaiming his eternal love for herself. The Count appears; in a desperate bid to save her lover's life Leonora offers herself to his rival on condition that Manrico be allowed to go free. The Count agrees. Unseen by him, Leonora swallows poison from a phial.
Scene 2 - The Prison of the Palace
Azucena and Manrico are together in the same cell in the hours before they are due to die. Azucena's fear of being burned at the stake has driven her to despair, and her son tries to comfort her by recalling their gipsy life in the mountains. Leonora comes to tell Manrico that he is free, but he will not leave alone, and suddenly realising how Leonora has gained his freedom, he rejects her; but the poison has already taken effect and as she dies Manrico understands the strength of her devotion to him. The Count appears as Leonora dies and orders Manrico to be taken immediately to execution. He drags Azucena to a window to witness his death, and as he is beheaded Azucena triumphantly reveals that Manrico was the Count's brother.