Pirro appears in the gallery to the sound of a festive march, and he and the wedding procession pass by (Chorus: "Premia, o Amore, sì bella costanza" / "God of love, reward this touching constancy"). Ermione swoons, but when her maidens and friends try to comfort her, she demands revenge. Oreste enters and tells her that he still loves her. She hands him a dagger and, trembling, he leaves to avenge her. She asks the gods to strengthen his arm, while Cleone and the chorus comment on her anguish (Chorus and duet: "Il tuo dolor ci affretta a consolarti ...Se l'amor mio ti è caro ... Incerto, palpitante ... Se a me nemiche stelle" / "We come to console you ... If my love is dear to you" ... "Uncertain, palpitating" ... "Unless, o gods, you are my enemies"). She rushes out in a fury, followed by the others.