Venice, 1742. Tito Amato has regained his zest for performing and is once again singing lead roles at the Teatro San Marco. On opening night, the famous castrato has the entire audience entranced—except for one box with its scarlet curtains stubbornly drawn. Annoyed at being ignored, Tito aims the full force of his golden throat at the fourth-tier box. He is astounded when the curtains part and a woman tumbles over the railing.

The victim is Zulietta Giardino, a mischievous courtesan involved with a young glass maker. Did a wager over a rival courtesan's jewels spell Zulietta's death? Or did the motive involve sinister events in the glass factories of Murano?

Tito faces troubles of a different sort at home. His upstanding neighbors regard his household as an immoral den of theatrical riffraff and disdain his wife, Liya, as an apostate Jew. While Liya attempts to reconcile with her disapproving family in the ghetto, Tito strives to be a good father to his adopted son.