We zip from A to Z again when we turn to Donizetti's last opera, the 1843 Dom Sébastien, Roi de Portugal. This is a sprawling French grand opera with an almost Hitchcockian ending. The title character, who is the king of Portugal, goes off to fight the Moors in 1578, and during the course of his mission sets free a Moslem girl, Zayda, who is about to be burned at the stake by the Inquisition despite her having been baptized a Christian. He brings her along with him to Morocco and returns her to her father, Ben-Selim - from whom she learns she is to be married to an Arab chieftain, Abayaldos. Abayaldos successfully leads his countrymen against Dom Sébastien's advancing Portuguese troops. Dom Sébastien survives the battle in which another Crusader has died in his defense. He is discovered alive by Zayda, who confesses that she loves him. She agrees to marry Abayaldos, on the condition that he safely return the wounded Dom Sébastien to Lisbon.
Back in Portugal, Dom Sébastien's nefarious uncle, Dom Antonio, has made himself regent upon hearing false news of his nephew's death. A movement is afoot to restore the throne to Dom Sébastien, but Abayaldos (in disguise) denounces him as an imposter; the Grand Inquisitor subsequently condemns Dom Sébastien and Zayda to death. Meanwhile, there has been a conspiracy to turn Portugal over to Spain, an act that would require the king's signature. Dom Sébastien refuses to sign the document, but then signs in the belief that it will save Zayda's life if he does so. He and Zayda, imprisoned in the Tower of Lisbon, descend by rope out its high windows. The Grand Inquisitor and Dom Antonio order their soldiers to fire upon the escapees, and the lovers die together as they fall into the harbor below.