Jack Hilliard hears a woman's voice singing an Italian aria and leans far out of the window, but he cannot make her out in the fog. The following day he tries to reach her through an advertisement. Finally they exchange notes, and he is invited to dine with her. He must go and come blindfolded. This he does, only to discover that she is masked. The following day she sails for Italy with the American Opera company, and from Naples mails Hilliard the mask. His old Italian servant Giovanni, whose daughter, betrayed by a prince, has died, wishes to return to Italy for revenge. Hilliard decides to accompany him. On the canal he meets the opera singer and she shows him her face only to beg him to cease his attentions. He discovers her next day trying to better the fortunes of her stranded opera company at Monte Carlo, and there he saves her from the forced advances of the Prince Monte Bianca. Later he goes to her villa and is pleasantly received by her. They are disturbed by the Prince whom Hilliard disarms only to learn he is the husband of the woman he loves. As the Prince rides from the gates he is set upon by Giovanni and killed. Thus the signorina, who never lived with her husband, and Hilliard, are free to love and marry.—Moving Picture World synopsis