Two of the opera's most memorable numbers are the tenor's serenade ("Apri la tua finestra") and the Hymn to the Sun ("Inno al Sole").

Iris, the young and innocent daughter of a blind old man, Il Cieco, lives happily, enjoying the sun and the simple things of nature.

During a puppet show, Osaka enters disguised as a child of the sun, singing the serenade "Apri la tua finestra [Open Your Window]", the most famous selection in the opera.

Before anyone, including the remorse-stricken Osaka who has returned, can stop her, Iris rushes back into the house and throws herself down a shaft leading to a sewer.

She quickly becomes delirious and imagines that she hears the voices of the three men, first Osaka, then Kyoto, and finally Il Cieco, each mocking her.