Paris, 1986. Partygoers mock the diplomat René Gallimard for his affair with a Peking Opera soprano. From his prison cell, Gallimard begins to tell his story.

Beijing, 1964. Gallimard is assigned to the newly-established French embassy. He goes to the opera and sees an enchanting soprano in the role of Madama Butterfly. He develops the fantasy that he is Pinkerton and Song Liling is Butterfly, the “Oriental” woman in submission to the “Western devil.” Gallimard’s boyhood friend Marc appears to him in a dream, congratulating him on his new love.

Gallimard visits Song at her flat. They drink tea together, but she sends him home. Her rebuff keeps him away from the opera for months. At last she writes to him, wishing to see him again.

The Ambassador, Toulon, informs Gallimard that he has been promoted to vice-consul. He goes immediately to Song’s flat to tell her the news.

Paris, 1986. Partygoers read more news about the Gallimard case.

Back in 1966, Toulon and Gallimard confer about America’s plans in Asia. Meanwhile, Comrade Chin of the People’s Liberation Army asks Song to serve the Revolution by passing on classified information from the French.

Gallimard is demoted because the Ambassador has lost faith in the Americans and in him. He goes to Song’s flat and demands that she strip for him. Then he relents … just in time for Song to announce to him that she is pregnant. Gallimard is aflame with joy: “I want to marry you!”

Song asks Chin to procure a male, blond mixed-race baby in seven months’ time. Toulon informs Gallimard that he is being sent home. Gallimard rushes to Song’s flat, intending to bring her back to France with him. The flat is deserted. An angry troupe of Revolutionary Chinese Opera performers takes the stage.

The Revolutionary Chinese Opera company stages a ritualistic denunciation of Comrade Song, the “actor-oppressor,” and recommends her rehabilitation. Chin orders her to go to Gallimard in France and send back weekly reports.

Gallimard, haggard, recalls his return to France ten years prior. Lonely, deflated and always haunted by Song’s memory, he would tell his story to anyone who would listen–but no one did.

Suddenly Song appears. Gallimard is transported by the reunion. Then two French counterintelligence agents come to arrest him on charges of espionage, claiming they have already extracted a confession from Monsieur Song. Before the audience’s eyes, Song is transformed from a woman in Chinese dress to a man in an Armani suit.

Song testifies in court. The judge asks whether Gallimard knew Song was a man. “You know, Your Honor,” Song replies, “I never asked.”

Song and Gallimard are left alone in a room in a prison. Song begins to strip. He will show René the truth. Gallimard protests that he only loved the lie. Declaring that he’d rather live in pure imagination, he sends Song away.

Dancers join Gallimard onstage and help him dress in kimono, wig and makeup. He is the Butterfly now.