Lieutenant B.F. Pinkerton is on shore-leave in Japan. He and his buddy Lieutenant Barton, out for a night on the town, stop in at a local establishment to check out the food, drink and girls, 'uh, and girls' to quote Lt. Barton. Pinkerton spies Cho-Cho San and immediately falls in lust. Barton counsels Pinkerton that he can 'marry' this beautiful Japanese girl, enjoy himself with cultural approval, then sail happily on back to America unshackled, since abandonment equates divorce in Japan. Barton assures Pinkerton that once abandoned, Cho-Cho will be free to marry whomever she chooses from amongst the Japanese people. When Pinkerton's ship sails out of port, Butterfly waits patiently for her husband to come home. Three years pass. Ever with her eye toward the harbor, Butterfly holds a secret delight that she eagerly wishes to surprise her husband with: their son. Pinkerton arrives in Japan with his American bride by his side. He goes to Butterfly to make his apologies and to finally end what Butterfly for three years has cherished in her heart.