René Gallimard, a sixty-five-year-old man, sits in a prison cell in Paris and tries to explain what he did and why. The action of the play takes place in the present time and includes Gallimard’s memories of earlier events.

As the play opens, Gallimard introduces his favorite opera, Madame Butterfly, by Puccini. In the opera, an American naval officer named Pinkerton purchases a wife, Cio-Cio-San, along with a house. Cio-Cio-San, or Madame Butterfly, falls in love with Pinkerton and bears his child, but he abandons her. In despair and sorrow, Madame Butterfly commits suicide.

Gallimard’s memory takes him back to 1960, in Beijing, China. At the house of the German ambassador, Gallimard, a minor French diplomat, hears Song, a Chinese male actor, perform the death scene from Madame Butterfly. Gallimard is deeply moved by the performance and its portrayal of pure sacrifice for love. As Song wears women’s clothing during the production, Gallimard believes Song is a woman. Gallimard compliments Song, who points out that the submissive Asian woman is a favorite fantasy of Western men. Song invites Gallimard to come to the Peking Opera and expand his mind. Gallimard takes Song up on the invitation and walks Song home after a performance.

Gallimard keeps returning and escorting Song home, until at last Song invites him in. Once inside Song’s apartment, however, Song gets nervous and explains that, as a Chinese girl, she is too shy and modest to see Gallimard alone. To make Song “his Butterfly,” Gallimard plays hard to get. He stays away from Song, who sends him increasingly desperate letters begging him to return.

Toulon, the French ambassador, promotes Gallimard to vice-consul, a position that puts Gallimard in charge of the intelligence division. His promotion gives Gallimard the confidence to visit Song. He asks Song directly to be his Butterfly and swears he wants honesty between them, with no false pride. Song answers yes. They caress each other and, to the music of Puccini, begin a love affair. Their passion ends Act One.

In Act Two, Gallimard and Song secure a flat in Beijing, where Gallimard visits Song several times a week. Song asks many questions about Western women and Western society as well as about Gallimard’s work. Ambassador Toulon, hearing the rumors about Gallimard and Song, has come to rely on Gallimard’s reports on Chinese public opinion. Meanwhile, Song secretly reports to Comrade Chin, a Communist Party official who is a woman. Song reports on what Gallimard knows about American troop movements in Vietnam. Comrade Chin disapproves of Song for wearing a dress during encounters with Gallimard and reminds Song that homosexuality is not allowed in China.

Gallimard and Song continue their affair for three years. At the same time, Gallimard continues having sex with his wife Helga, who hopes to conceive a child. Gallimard also has an affair with Renee, a sexually uninhibited young student. Renee is too aggressive for Gallimard’s tastes, but Gallimard’s affair with her does give him the confidence to make a new demand of Song: He wants to see his Butterfly naked. Song reacts to this request with horrified modesty. Gallimard begs Song to forgive him. Then Song tells him Song is pregnant. When Gallimard hears this news, he immediately wants to marry Song. Song leaves town for several months and later returns with a baby boy.

Outside events unexpectedly end the love affair. The Cultural Revolution turns people against Chinese opera actors and other intellectual elites. Song and Gallimard lose their flat. Meanwhile, the Vietnam War proves that Gallimard’s intelligence gathering is faulty. Gallimard gets demoted and sent back to France. Song is sent to a reeducation camp, tortured brutally, forced to confess to a homosexual act, and compelled to star in a propaganda film denouncing anti-Revolutionary behavior. Song serves four more years of time on a rural commune before receiving a new assignment: to return to Paris, reconnect with Gallimard, and resume spying. Back in Paris, Gallimard has divorced his wife, so when Song arrives in Paris, Gallimard claims Song as his new wife. At the end of Act Two, Gallimard believes his affair with Song will resume. But Song, addressing the audience, asks them to stretch their legs and wait for a change.

Act Three begins in a courtroom in Paris in 1986. Song testifies to the court, dressed in a men’s suit. Song describes the “very comfy life” that Gallimard has provided for Song and the boy. Song also tells the court how he urged Gallimard to take a job handling sensitive documents and persuaded Gallimard to photograph them for transmission to the Chinese embassy. Song’s testimony about their affair backs up Gallimard’s claim that he thought Song was a woman. Song explains to the judge that men always believe what they want to hear and lectures the court about the “international rape mentality” of the West toward the East. The judge asks Song directly if Gallimard knew Song was a man. Song replies, “I never asked.”

Back in Gallimard’s prison cell, Gallimard recalls Song’s testimony in court and suffers great shame because of it. Against his will, Gallimard’s mind transports him back to the night he met Song. Song appears in the prison, but in male dress. Song assumes female postures and tempts Gallimard again, trying to make Gallimard see that his “Butterfly” was always an illusion. Then, Song at last grants Gallimard’s often-repeated request and starts to strip. Gallimard begs Song to stop, but Song drops his briefs. Gallimard responds to the sight of a naked Song with hysterical laughter because Song is “just a man.” Song responds that he’s not just any man, but the person Gallimard has loved for years. Gallimard rejects Song because of twenty years of betrayal.

In the last scene of the play, Gallimard returns to the idea of his perfect woman. As dancers appear and help him make up his face, Gallimard reprises his vision of Asian women who die because they love foreign devils. He admits that he has long since faced the truth that Song is a man and that love for Song warped his judgment. Now, when Gallimard looks in the mirror, he sees nothing but a woman. In Gallimard’s fantasy world, a woman sacrifices herself for the love of a man. Gallimard dons a kimono and wig and becomes Madame Butterfly. The music from Puccini’s death scene blares as Gallimard plunges a knife into his own body and commits suicide. As the lights fade slowly to black, Song stands smoking a cigarette and stares down at Gallimard’s body. Song asks, “Butterfly? Butterfly?”