Bradamante disguises herself as her own brother Ricciardo, and sets out with her tutor Melisso to rescue Ruggiero. Morgana, Alcina’s sister, falls in love with “Ricciardo,” although she is betrothed to Alcina’s general, Oronte. Oberto, a young boy, asks “Ricciardo” and Melisso to help him search for his father, also taken captive by Alcina. Ruggiero recognizes “Ricciardo” as Bradamante’s brother, but remains under Alcina’s spell. Oronte discovers Morgana’s infatuation with “Ricciardo.” Betrayed, Oronte maliciously tells Ruggiero that Alcina is in love with “Ricciardo.” Alcina denies the accusation and vows to transform “Ricciardo” into a wild beast. To save herself, “Ricciardo” sends Morgana to Alcina to say that “he” loves another. Morgana rejoices, thinking “Ricciardo” loves her, and “Ricciardo” escapes.

Ruggiero realizes he is the victim of enchantment. Melisso puts a magic ring on Ruggiero’s finger that breaks Alcina’s spell. “Ricciardo” reveals herself as Bradamante; Morgana and Ruggiero successfully entreat Alcina not to transform “Ricciardo.” Alcina is distraught when Oronte reveals that Ruggiero is planning to escape. Ruggiero, now reunited with Bradamante, bids the magic realm farewell. Alcina commands the spirits to thwart Ruggiero’s escape, but they do not obey her.

Morgana returns to Oronte, who takes her back after first rejecting her. Alcina confronts Ruggiero and accuses him of infidelity. After learning that Ruggiero is betrothed to Bradamante, Alcina is torn between love and vengeance. With Melisso and Bradamante, Ruggiero plans his escape and vows to defeat Alcina’s forces. After hearing about Ruggiero’s victory from Oronte, the sorceress threatens to free the entire realm. Alcina tries to detain Ruggiero and Bradamante, but Ruggiero destroys the source of Alcina’s power and returns to reality.