After an absence of three years, Pinkerton has returned to Nagasaki, where he had lived with Butterfly, his Japanese wife. In the intervening time, he has returned home to America and married again and is now in Japan to claim his son. When he sees evidence of Butterfly's loyalty, he realises how cruel he has been. Unable to stay there any longer, he sings a heartfelt farewell to the house where he was so happy. He knows he is a coward, but cannot bear to stay.