Nagasaki, 1900. Pinkerton marries Butterfly lightly, almost as an exotic game. The consul Sharpless tries to caution him: she is serious, she truly believes in this. Pinkerton laughs. That night, in the moonlight, the two sing of their love. It is the opera's most beautiful scene — and the most poisoned, because we already know how it will end.

Three years later. Pinkerton is in America. Butterfly has a child — his son. Suzuki no longer believes he will return. Butterfly is unshakeable: he will come back. Sharpless brings a letter from Pinkerton, tries to read it — Butterfly will not let him finish, she is too happy just hearing his name. Then an American ship appears in the harbour. Butterfly, Suzuki and the child wait all night at the window.

At dawn, Pinkerton has arrived — but he is not alone. With him is his American wife, Kate. Suzuki must tell Butterfly the truth. They want the child, to take him to America. Butterfly understands everything in an instant. She asks them to return in half an hour. She holds the child, lets him play with a doll and an American flag, blindfolds him. Then she takes the dagger with which her father had taken his own life. She kills herself. Pinkerton bursts in calling her name. It is too late.