Nagasaki, at the beginning of the twentieth century.
Young Lieutenant B.F. Pinkerton inspects his newly leased house, which comes complete with a wife, Cio-Cio-San, and her servant, Suzuki. The American Consul, Sharpless, listens as Pinkerton muses about Cio-Cio-San, the delicate butterfly who has struck his fancy, and mentions his intention to have a “real” American wife in the future.
Butterfly and her friends arrive in happy anticipation of her wedding to Pinkerton. Butterfly tells him that she has secretly adopted the Christian faith so that they might be closer to one another. The marriage deed is signed. As Pinkerton lifts his glass in toast to the union, Butterfly’s uncle, the Bonze, a Buddhist priest, bursts in and denounces her for renouncing their religion. The family disowns Butterfly and leaves. Pinkerton reassures Butterfly as she tries to forget her uncle’s curse. As night falls, the newlyweds ecstatically consummate their love.
--- INTERMISSION ---
It has been three years since Pinkerton left Nagasaki. Butterfly has borne a son and is virtually penniless, but she remains hopeful and, in the aria “Un bel dì,” assures the skeptical Suzuki that Pinkerton will return.
Goro, a marriage broker, seeks to persuade Butterfly to marry his client, the wealthy Prince Yamadori. Goro reminds Butterfly that Pinkerton’s desertion constitutes divorce in Japan. Butterfly insists she is still married under the law of her husband’s country. Sharpless, who has come to read her a letter he received from Pinkerton, is dismayed by her blind faith, and quietly reveals to Goro and Yamadori that he has come to prepare her for the fact that Pinkerton is returning to Japan but not to be her husband. Goro and Yamadori depart in frustration.
Sharpless begins to read the letter to Butterfly, but she misconstrues its meaning. Sharpless privately curses Pinkerton and then bluntly asks Butterfly what she would do if Pinkerton did not return. She answers that she could return to her life as a geisha or, better yet, die. Sharpless urges her to accept Yamadori’s proposal. Shocked, she orders the Consul to leave, but then proudly presents Pinkerton’s son, whom she now calls “Sorrow.” When Pinkerton returns, she tells Sharpless, Sorrow will be called “Joy.” Sharpless promises to inform Pinkerton of his son’s existence.
The roar of a cannon from the harbor restores Butterfly’s confidence. Pinkerton’s ship is coming to port. Butterfly, motionless as a statue, waits for him to arrive.
At dawn, Butterfly retires. Pinkerton and Sharpless finally arrive. Sharpless requests Suzuki’s help in persuading Butterfly to give up her child. Pinkerton is overwhelmed with remorse and leaves.
Butterfly enters the garden, eagerly searching for Pinkerton. The moment she sees an American woman, Kate, she understands that Pinkerton is married and has come to take away her son. Butterfly wishes Kate happiness and with great dignity agrees to relinquish the child, but only if Pinkerton comes for him.
Butterfly orders the room darkened, prays to the Buddha, and prepares to die. She reads the inscription on her father’s dagger: He dies with honor who cannot live with honor. After saying goodbye to her son, Butterfly commits the sacred rite of hara-kiri. As she dies, Pinkerton approaches the house, calling her name.