When handsome, successful Domenico (Marcello Mastroianni) first meets the sexy young waif Filumena (Sophia Loren) in Naples during World War II, he is instantly smitten. Flash forward to the postwar years, and the two meet again, sparking a passionate affair that spans two decades. But when Filomena -- who has now become Domenico's kept woman and has secretly borne his children -- learns that her lover is planning to wed another, she stops at nothing to hook him into marrying her instead.