Jerusalem, which is under the rule of the Saracen King Argante, is besieged by the Crussader army led by Goffredo of Bouillon. Almerina, Goffredo's daughter, and the daring knight Rinaldo are engaged to be married. Argante awaits assistance from the Queen of Damascus, the sorceress Armida, and she abducts Almerina in order to distract Rinaldo from involvement in the siege of Jerusalem.
Goffredo and Rinaldo set out to find Almerina, with whom Argante is in love. Armida is captivated by Rinaldo, buth the knight spurns her. Goffredo and the knight Eustazio attempt to gain access to the queen's enchanted castle, the entrance to which is guarded by fire-breathing dragons.
Armida, who has tried in vain to tempt Rinaldo, is now intent on killing Almerina. Rinaldo saves his beloved's life. Goffredo and Eustazio arrive and with the assistance of a good magician lay waste to Armida's garden. There ensues a decisive battle between Goffredo's forces and the army of Argante who is aided by Armida's spells. Goffredo is victorious – nothing will interfere with Almerina and Rinaldo's marriage, and Argante and Armida who have been taken prisoner are graciously released and embrace Christianity.