Act I

Outside a little house overlooking the Nagasaki harbor, Pinkerton, an American naval officer, is making the final arrangements with the marriage broker, Goro, for a Japanese wedding. According to law, the marriage will not be binding, and Pinkerton revels in the carefree arrangement. The American Consul, Sharpless, warns Pinkerton that his bride, Cio-Cio-San (called Butterfly by her friends), is serious about the marriage.

Butterfly and her relatives arrive. She tells Pinkerton about herself, her family and her age – which is only 15 – and shows him the few possessions she has brought, including the ceremonial dagger with which her father killed himself. The brief ceremony is performed and as the celebration begins, an ominous figure appears. He is Butterfly’s uncle, the Bonze, a Japanese priest, who curses Butterfly for abandoning the Japanese gods in favor of Christianity. All the relatives side with the Bonze, and they turn on the young bride. But Pinkerton orders them all away, and in the long and tender love duet that closes the act, Butterfly forgets her troubles. Together, Pinkerton and Butterfly enter their new home.

Act II

Part one  Three years have passed since Pinkerton sailed for America, but Butterfly remains loyal and describes to Suzuki her dream of his return. Sharpless, knowing that Pinkerton has taken an American wife and will soon be arriving in Nagasaki with her, attempts to prepare Butterfly for the shock, but she is too excited by news of Pinkerton’s return to listen. Goro enters with the wealthy Prince Yamadori, who is courting Butterfly. When Goro and Yamadori leave, Sharpless gently advises her to accept the Prince. That is out of the question, she insists, and she brings in the reason for that impossibility – her young son, named Sorrow. But, she adds, he will be called Joy when his father returns. Defeated, Sharpless leaves, promising to tell Pinkerton of the boy.

Part two  A cannon is heard, and Butterfly and Suzuki see Pinkerton’s ship coming into the harbor. Butterfly jubilantly prepares for his return, filling the room with flowers and again donning her bridal costume. As night falls, Butterfly, Suzuki and the child wait, motionless.

Part two  Dawn finds Butterfly, Suzuki and Sorrow just where they were at the close of the last scene, except that the maid and the child are fast asleep. Butterfly takes her sleeping son into another room, singing him a lullaby.  Sharpless enters with Pinkerton and his wife, Kate. Suzuki almost at once realizes who this is. She cannot bear to tell her mistress, and neither can Pinkerton. He sings a passionate farewell to his once-happy home, and leaves. But Butterfly, entering, sees Kate and realizes the painful truth. With dignity she tells Kate that she may have her boy if Pinkerton will come soon to fetch him. Left alone with the child, she makes an agonizing farewell, blindfolds the boy and goes behind a screen where she stabs herself. Pinkerton comes rushing back, but it is too late.