Lisa, Alessio, Elvino and the villagers are in the square. Elvino declares that he will renew his vows and proceed to marry Lisa. She is delighted. As they are about to go to the church, Rodolfo enters and tries to explain that Amina is innocent because she did not come to his room awake – she is a somnambulist, a sleepwalker: (Duet, first Elvino / "I cannot deny, my lord, what my eyes have seen"; then Rodolfo / "Certain people when they sleep go about as if awake".) Elvino refuses to believe him and calls upon Lisa to leave, but at that moment Teresa begs the villagers to be quiet, because Amina has at last fallen into an exhausted sleep.