In Nagasaki, in a house on a hill, the marriage of Cio-Cio-San (Madama Butterfly) to the American officer Pinkerton is celebrated. The Consul Sharpless brings to his attention that the young bride takes her marriage very seriously and Pinkerton only sees it as an amusement. Indeed, when her family repudiates her for this relationship, the young woman finds in Pinkerton’s love a comfort that doesn’t look like a mere play.
The wedding is a terse ceremony, more a business deal than an exchange of vows. The post wedding celebration is interrupted by the arrival of the Bonze, Cio-Cio-San's Uncle, a Buddhist priest who berates the young girl for betraying her people and her religion. Pinkerton angrily orders the Bonze away and then turns to his new wife to console her, drying her tears and reminding her night is approaching. She lost her family but anyway she is happy with her husband.
Three years of waiting have passed from her marriage, but Butterfly still hopes that Pinkerton will return. She trusts the love vows and doesn’t understand the advices of the United States Consul, who has the mission to notify her about Pinkerton’s arrival. Yamadori, who came to ask her to marry him, interrupted the discussion. The young woman refuses him. Sharpless tells the truth to Butterfly: Pinkerton will never come back to her and will be better for her to accept the proposal. She disappear and after several minutes, she comes with a wonderful little boy. She is raising their son and refuses any other proposal for marriage. A cannon shot herald announces the boat arrival. She prepares the house for him. She is waiting for him but Pinkerton does not come to their house because he is married with an American woman, Kate.
After a night of waiting, Butterfly falls asleep at dawn. Pinkerton arrives together with the Consul and Kate, his American wife, and tells Suzuki, the maid, the purpose of their visit, to take his son. Butterfly takes the news with a lot of courage. While the little one waits for his father, Butterfly commits suicide, hearing announces her name called one last time by Pinkerton, who climbs the hill in a hurry.