Set in 1904 Nagasaki, Japan, American Naval officer B.F. Pinkerton arranges a marriage to Cio-Cio San, a 15 year old Geisha nicknamed "Butterfly." Thee years later, after Pinkerton's return to the U.S., Cio-Cio San clings to the hope that her beloved will return. She prepares and "American home" in anticipation of Pinkerton's return with her maidservant Suzuki. Sharpless, the American Consul, receives word of Pinkerton's return to Nagasaki and attempts to brace Cio-Cio San for Pinketon's return with his new American wife. Cio-Cio San reveals that she bore Pinkerton's child following his departure from Japan. Sharpless promisses to share this news with Pinkerton, who in turn agrees that he, along with his new American wife Kate, will adopt the child.