Floria Tosca sings this aria to Scarpia about the nobility of being an actress and a human being. This after Scarpia threatens to kill Cavaradossi if she does not submit to him. This is one of Maria Callas’ greatest performances, one which she brings out the deep anguish her character is going through. She takes things into her own hands and kills Scarpia after she gets a written promise from him to release Cavaradossi. What she doesn't know is that Scarpia tells his henchman to carry things out like with another prisoner in a similar situation--the fake bullets replaced with the real ones!