Act One - Magdalena's Inn in the Vale of Roncal, Navarra, 1697. The Preludio, based on the main themes from the work, leads into the first scene. Women are spinning, the men are drinking and playing cards with the local Curé and the young shepherd Tomillo, a lodger at the Inn (Coro y solos: "Al amor de la lumbre".) His sweetheart Rosalía, Magdalena's daughter, is prevailed upon to sing the tale of the beautiful Princess Zulima, daughter of a Moorish King of Granada, whose Christian lover contrived to bear her away from the Alhambra, with the miraculous aid of the Virgin (Canción: "Pues señor, este era un rey".) Tomillo would have preferred a story of ghosts and witches, but the Curé reminds him that such tales are dangerous, and forbidden by the Inquisition. Tomillo says that is nonsense - he has seen a witch with his own eyes this very day. In a long tale, he tells the company how he carried the old Witch that lives up at the castle over a creek on his back, and was rewarded by a blessing, and a gold doubloon. To the Curé's horror, he defends the Witch, who has saved a sick child and does nothing but good. Eventually, the Curé leaves with the chorus to settle down for the night (Coro: "La triste queda ya sonó".) Romance is different from real life. The lodger is about to be thrown onto the street, for Magdalena would rather put her daughter in a convent than entrust her to a vagabond like Tomillo. She tires herself out shouting and falls asleep, giving the young lovers the chance to flirt together (Terceto y dúo: "Chito, que ya mi madre - Hora que en calma".) Magdalena sneezes and wakes up, telling Tomillo once and for all that if he cannot raise at least a hundred doubloons like the one he got from the witch, he will never marry her daughter.
Leonardo, Magdalena's stepson and heir to the inn, comes in fresh from the hunt. He explains to Tomillo why he has been so distracted lately. Sleeping off the rigours of the hunt on the riverbank, he had a vision of a beautiful woman bathing. Following her as in a dream, she fled into the forest, but since then he cannot get her beauty out of his mind (Relato de aparición: "En una noche plácida"). Tomillo tells him to forget his dream, but Leonardo assures him that the Witch has told him that he will win both his love and his fortune. Then Leonardo has spoken with the witch too? Yes, she cured him from a fever he contracted after seeing his vision, and comes to help him every time he blows three blasts on his horn. When Leonardo dozes, Rosalía creeps in to ask Tomillo how they should avert her mother's threat. Tomillo bravely steals Leonardo's horn and sounds it three times, before his friend is awake enough to stop him.
The old Witch materialises. Although initially displeased at Tomillo's presumption in summoning her, given a good character reference from Leonardo, she agrees to help the couple, producing a bag of gold from thin air containing the necessary hundred doubloons and more. Leonardo is strangely moved by her kindness, and Tomillo and Rosalía offer extravagant thanks before they leave (Cuarteto: "Cual siempre a tu llamada".) The Witch tells Leonardo her story: how as a young girl at court she attracted the attentions of four noble suitors, but rejected them all. In revenge, they paid a witch to enchant her by adding their combined ages to her own. She therefore looks 118 years old, though her heart is still that of a young girl of 16. The witch was unable to undo the enchantment, but took pity, promising her that if a young man swore to do great deeds in her name and for her love alone, she would regain her rightful shape. (Dúo: "!Así, así te quiero yo!") If Leonardo will go to fight for the Spanish army in Italy he may win fame and fortune, and free her from the enchantment. She will give him a ring to show to the General, the Duke of Savoy, to help him on his way. Leonardo agrees, though deeply regretful at having to leave the land where he had thought to live and die (the beautiful solo: "Adiós, risueños campos".) He will gain her release, or lose his life in the process.
The Witch hears musicians approaching to celebrate the union of Tomillo and Rosalía, and disappears up the chimney. The happy couple enter with the mollified Magdalena, inviting the villagers to join in the celebrations (Solos y coro: "!Seña Madalena, venid por acá!".) Leonardo tells Tomillo that tomorrow he must leave for the wars, much to everybody's surprize. He sings the famous Jota navarrese, in melancholy praise of the homeland he must leave, before the joyful celebrations bring the curtain down in energetic song and dance (Jota: "!Ay, canto alegre de mi país!".)
Act 2 - the Village, two years later. The villagers are celebrating the midsummer Fiesta, and the bells of the little church ring in honour of the Virgin. (Coro: "Hoy todos celebran".) Tomillo emerges from the church praying God to stop sending him children - Rosalía is so fertile she's already provided him with three, at regular nine month intervals, since they married. The villagers congratulate the happy parents and "Granny" on their luck, and Magdalena invites them back to the Inn to celebrate after the festive Pelota game which is about to take place. Some of the people have heard of the King's sickness. He has apparently been enchanted, and they wonder whether their local Witch in the castle above the village might be responsible. Tomillo defends her stoutly, and everyone agrees she has done them nothing but good. After the opposing teams of Roncal and Biscay sing together in friendly rivalry (Coro: "En la plaza de la gente") the villagers leave to watch the game.
Leonardo appears. Now a brave Captain, he sings of his joy at finding his village unchanged (Romanza: "Todo está igual".) Tomillo comes in, and Leonardo tells him how the Duke of Savoy received him, and how he has proved himself worthy of the love of the Witch, whose story was evidently known to the Duke. Relieved that all seems well with her, he leaves for the castle by a shortcut, promising Rosalía and Tomillo to return soon. The villagers celebrate the victory of their team with a song, though the following dance (a zortzico) is briefly interrupted by the arrival of an Inquisitor and six constables, asking the way to the Curate's house (Coro, solos y danza: "Al cabo los del pueblo"). The Curate unwillingly tells the villagers to guide the Inquisitor to the castle, to arrest the Witch. As they leave, Tomillo and Rosalía quickly take Leonardo's shortcut to try and warn their benefactress.
Scene 2. Leonardo arrives at the castle and blows his horn. The witch comes out, delighted that her champion has succeeded in his quest to free her. As they sing happily together, she feels her blood stirring and her youth returning (Dúo: "Circula en mis venas".) Their joy is interrupted by the arrival of Tomillo and Rosalía, who warn the Witch about the approach of the Inquisitor and his minions. She retires into the castle as the Inquisitor's party arrives. When he calls for the castle to be opened in the name of the Holy Office, a beautiful young woman, dressed in white, appears. It is the Witch, transformed back to her proper shape as Blanca de Acevedo, who chose to live here in her ruined family castle rather than go into hiding when she became bewitched. The Inquisitor says she must answer the accusations of witchcraft, and she hands herself over to him, warning the frantic Leonardo to put his faith in God's mercy. Blanca is taken away to the city of Pamplona, leaving Leonardo and his friends in despair as the curtain falls (Final: "Quien defenderla intente".)
Act 3 - deep in the citadel of Pamplona, two night's later. Army officers are enjoying a drinking bout to celebrate the peace, and though Leonardo feels very far from happy he leads them in a Brindisi: "La dicha y la calma". Leonardo and his fellow officers discuss the grave illness of the King. They all support the candidacy of the "enlightened" Bourbon claimant the Duke of Anjou against the superstitious Austrian Hapsburg faction, and the Inquisition, and Leonardo tells them that Blanca has been condemned to penance for life as a nun in a nearby convent. The officers offer to help him rescue her before she takes her final vows.
Rosalía and Magdalena arrive in haste. They have been unable to see Blanca or get word to her, but have discovered from the well-disposed Sacristan that the whole convent is in a hysterical uproar due to Blanca's arrival. The Sacristan has told the Mother Superior that a Holy Friar is on his way to exorcise the girl, and when Tomillo arrives - also disguised as a friar - the conspirators are ready to head for the convent. Leonardo is to visit Blanca as the Holy Man, and assure her that help is on the way, leaving the rest to Tomillo. The four disperse as the soldiers return, to celebrate the evening retreat with a rousing "Rataplan" chorus (Coro: "Retírase el soldado".)
Scene 2 takes place in the cloister of the convent, that night. The Mother Superior enters Blanca's cell as the young pupils and their teachers pray that the devil may be cast out of their convent. The girls whisper about a demon and three witches who have been seen around the convent (Coro: "¡Ay, qué miedo me da!") and one of them has seen the cause of all the commotion - a pretty, pale girl, dressed in black, and crying incessantly. The Mother Superior emerges from the cell. She tells the pupils they cannot speak to the possessed girl until the Holy Friar has exorcised her demons, and they leave. Tomillo, still in his friar's habit, comes in with Rosalía and Magdalena, bearing a letter for the Mother Superior from one "Padre Celestino", asking her to accept Rosalía as a postulant. They discover the exact whereabouts of Blanca's cell, as the pupils announce the Holy Man's arrival - Leonardo, dressed as a Franciscan. Explaining he must be alone with the girl, he enters the cell (Coro y solo: "Aquí ya está el padre"). Blanca feels that everything is hopeless and she must submit to becoming the Bride of Christ, but Leonardo tells her to have faith in his love. They sing of their love, whilst Tomillo leads the prayers for Blanca's soul and reports to the nuns on the progress of the "exorcism" (Terceto y coro: "Ven, que mi amor immenso".)Leonardo comes out, and tells the Mother Superior to leave the purified Blanca to her meditations before leaving. Tomillo frightens the girls by telling them that now Blanca's demons are on the loose, they'd better watch out that night. The Mother Superior says she will decide on Rosalía's petition the next morning, and asks her and her mother to stay overnight with Tomillo in the Sacristan's lodge, within the convent walls. The Mother Superior and the pupils retire, nervously, to their cells.
Blanca is praying alone in her cell (Solo: "Inquieto late el pecho mío".) A bell rings, and the frightened pupils stick their heads out of their doors. It must be the witches - so they quickly slam and lock their doors. Tomillo, Rosalía and Magdalena enter disguised as witches. They sing and dance to frighten the girls thoroughly before knocking three times on Bianca's door. She comes out draped in black, and the "witches" whisk her through the sacristan's lodge and out of the convent. (Terceto y coro: "¡Zahorí! ¡Zahorá!".) As soon as they are safely out of the way, the pupils rouse the Mother Superior and the nuns, telling them that Blanca has been spirited away by three witches. The Mother Superior orders the nuns to ring all the bells and call the Sacristan, but they are interrupted by a cannon shot from the citadel. Captain Leonardo enters with Tomillo and a troop of soldiers. He tells the Mother Superior that the cannons are announcing the death of the old King. He requests the nuns to pray for the new king, Felipe V, and when the Mother Superior implores him to help find the girl who has been captured by the witches, Leonardo tells her that the age of witches and ghosts is over - the girl who occupied the cell was the last ever witch, and the Age of Enlightenment has arrived! The nuns disperse to pray for the soul of the late King, and the curtain falls to the strains of the Inquisitor's theme from the previous act (Final orquestral.)