Set in legendary medieval Europe around the time of Charlemagne, Alcina’s libretto was adapted by Antonio Marchi from Ludovico Ariosto’s 16th-century epic poem Orlando furioso. Alcina is a Circe-like sorceress who lures men to her enchanted island, then turns them into wild beasts or inanimate objects once she tires of them.
Act I. Disguised as her brother Ricciardo, Bradamante, escorted by her tutor Melisso, has landed on Alcina’s island in search of her missing fiancé, Ruggiero. They encounter Alcina’s pretty sister, Morgana, who immediately falls in love with “Ricciardo.” The barren island is suddenly transformed to reveal Alcina’s magnificent palace, where she is surrounded by her courtiers and her new lover Ruggiero, who has forgotten Bradamante and is completely captivated by the sorceress.
Alcina’s general, Oronte, appears, furious that his beloved Morgana has fallen for Ricciardo/Bradamante and challenging “him” to a duel. He reveals the terrible things Alcina does to her discarded suitors.
Bradamante angrily reveals her identity to Ruggiero, but—spellbound by Alcina—he refuses to believe her and challenges this supposed rival.
Morgana begs Bradamante to flee this dangerous realm.
Act II. Melisso accuses Ruggiero of betrayal of his knightly duties because of his enslavement to Alcina. He gives the young man a magic ring that undoes his enchantment and brings him back to his senses. Melisso instructs him to pretend he is still in love with Alcina, but to prepare to leave her. Bradamante again reveals her identity to Ruggiero, but he still doesn’t believe her, thinking this is another one of Alcina’s spells. At the palace, Alcina is preparing to turn Ricciardo into a wild beast to placate Ruggiero, but is stopped by Morgana and later Ruggiero. Ruggiero asks Alcina’s permission to arm himself and go hunting while assuring her he still loves her. Oronte arrives and tells Alcina that Ruggiero is trying to escape. Alcina, who truly loves Ruggiero, is in despair. In her subterranean chamber, she calls on demons to aid her in keeping Ruggiero, but her magical powers fail her and she destroys her wand.
Act III. Now knowing Ricciardo’s true identity, Morgana tries to rekindle her love with Oronte. Alcina and Ruggiero meet by accident; he admits he wants to leave her, revealing his love for Bradamante. Alcina reacts in fury. Ruggiero, Bradamante, and Melisso fight Alcina’s warriors and beasts.
Oronte announces their victory to Alcina; she admits she is now powerless to oppose them. After some hesitation, Ruggiero finally shatters the urn containing the source of Alcina’s powers, and she and Morgana vanish with a cry. The palace crumbles into dust, and the enchanted beings are returned to their human forms. All join in a dance to celebrate their release and the destruction of Alcina’s evil magic.