A convent in Naples is home to several secular residents, much to the dismay of the prioress. The convent is to be the setting for a musical performance featuring the famous opera singer Farinelli. The young and beautiful Inez has been placed in the convent by her ambitious father and is to sing a part with Farinelli. For the occasion, she wears the precious jewels of Saint Cecilia. But outside Naples, a pirate ship is anchored, and the pirates have secretly mingled with the churchgoers.