Setting: The Orient Express during the 1920s
Konstanze, Blonde (her English maid) and Pedrillo (the valet of Konstanze's fiancé Belmonte), have been taken captive by pirates and sold to Pasha Selim. After searching for months, Belmonte has learned they are being held captive inside the Pasha’s private car aboard the Orient Express, which is ready to depart from Istanbul for Paris.
Belmonte searches for Pasha Selim’s private train car, yearning for his reunion with Konstanze. He meets the Pasha’s overseer Osmin, who refuses to answer Belmonte’s persistent questions, and the mention of Pedrillo (whom Osmin believes is his rival for Blonde) enrages Osmin. Pedrillo approaches Osmin with a proposal of peace between them, but Osmin refuses. Belmonte returns and finds Pedrillo, who tells him the story of how he and the ladies came to be in the Pasha’s possession. He reveals that Pasha Selim is in love with Konstanze but that she remains true to her beloved in spite of the Pasha’s advances. Belmonte and Pedrillo begin to plan an escape. Konstanze appears with the Pasha and they are heralded by the crowd at the Istanbul station. Pasha Selim attempts to console Konstanze and assures her of his love. Konstanze relives her past love and protests that she will remain true to Belmonte. Pasha Selim admits that he loves her even more for her resistance, and that he will not use force—for he, too, knows love. Pedrillo introduces Belmonte to the Pasha as a gifted young architect, and Selim approves. They try to slip past Osmin, who tries to stop them, but the two succeed in getting into the Pasha’s car.
Blonde scolds Osmin and instructs him in the correct way to treat European women. Osmin orders her to love him, for that’s the way it’s done in Turkey. She maintains that an English woman is beholden to no man, and that she surely prefers Pedrillo. Blonde reminds him that her mistress is the Pasha’s favorite, and that she enjoys their protection. Osmin warns Blonde not to flirt with Pedrillo. She mocks him and threatens to scratch out his eyes. Meanwhile, Konstanze mourns her separation from Belmonte. The Pasha reminds her that by the next day she must decide whether to accept his offer. She maintains that she can honor him but never love him. Pasha Selim wonders if perhaps Konstanze has so much courage because she plans to escape, or if she is hiding her true feelings. Pedrillo tells Blonde of Belmonte’s arrival and describes the plan for the “abduction.” They will get Osmin drunk, slip him a sleeping potion, and all four lovers will escape. Blonde is delighted and looks forward to telling Konstanze of Belmonte’s arrival. Pedrillo goes to work on Osmin, telling him that Mohammed should not have forbidden drinking. Osmin finally succumbs to temptation and joins Pedrillo in praising wine and women before falling asleep. The coast is finally clear for the reunion. Belmonte at last sees Konstanze. The happy reunion darkens when Belmonte and Pedrillo jealously question the women’s faithfulness, but misunderstandings finally melt into relief and joy.
Pedrillo gives the signal for escape. When the women appear, the noise awakens Osmin, who sends for the guards. The lovers are trapped, and Osmin will not accept Belmonte’s bribe to keep silent. Instead, Osmin savors the prospect of torturing and killing his enemies. The Pasha is informed of the treachery and arrives to question the prisoners. While Konstanze offers to die to save her beloved, Belmonte suggests that the Pasha could collect a ransom from his wealthy family, the Lostados. Selim then realizes that Belmonte is the son of an old enemy and orders them to prepare for a punishment such as Belmonte’s father would have dealt. Belmonte and Konstanze vow to welcome death as the path to an eternal union. The Pasha decides that rather than taking revenge, he will free all of the captives, for he despises Belmonte’s father too much to imitate him. He bids Belmonte return to his homeland. This magnanimous act confounds Osmin, who protests the loss of Blonde, to no avail. The Pasha declares that love cannot be won by force. As the train pulls into the Paris station, the lovers vow never to forget the Pasha’s kindness. Osmin’s rage erupts, but he is silenced by the crowd chanting praise to Pasha Selim.