When the composer Pietro Cignoni meets Sylvia and Lyda, the daughters of barrister Gio Romano, he and Sylvia fall in love and eventually marry. Sylvia is unaware of how jealous her younger sister is. Even more jealous is the organist Rosni who for years has adored Sylvia in silence, not daring to ask her to marry him because he is a hunchback. Together Sylvia and Pietro enjoy five years of wedded bliss and are happy with their darling daughter, Renée. Then Sylvia notices that her eyesight is gradually failing and learns that only an operation can perhaps save her from total blindness.