Scene 2. The village, near Teresa's mill. Water runs through the race and the wheel turns rapidly. A slender wooden bridge, spanning the wheel, gives access from some dormer lights in the millroof to an old stone flight of steps leading down to the foreground.
Lisa has been making hay while the sun shines. She has induced Elvino to promise to marry her. Preparations for the wedding are on foot. The villagers have assembled. Rodolpho endeavours to dissuade Elvino from the step he is about to take. He explains that Amina is a somnambulist. But Elvino has never heard of somnambulism. He remains utterly incredulous.
Teresa begs the villagers to make less disturbance, as poor Amina is asleep in the mill. The girl's foster-mother learns of Elvino's intention of marrying Lisa. Straightway she takes from her bosom Lisa's handkerchief, which she found hanging over Rodolpho's bedpost. Lisa is confused. Elvino feels that she, too, has betrayed him. Rodolpho again urges upon Elvino that Amina never was false to him—that she is the innocent victim of sleepwalking.
"Who can prove it?" Elvino asks in agonized tones.
"Who? She herself!—See there!" exclaims Rodolpho.
For at that very moment Amina, in her nightdress, lamp in hand, emerges from a window in the mill roof. She passes along, still asleep, to the lightly built bridge spanning the mill wheel, which is still turning round quickly. Now she sets foot on the narrow, insecure bridge. The villagers fall on their knees in prayer that she may cross safely. Rodolpho stands among them, head uncovered. As Amina crosses the bridge a rotting plank breaks under her footsteps. The lamp falls from her hand into the torrent beneath. She, however, reaches the other side, and gains the stone steps, which she descends. Still walking in her sleep, she advances to where stand the villagers and Rodolpho. She kneels and prays for Elvino. Then rising, she speaks of the ring he has taken from her, and draws from her bosom the flowers given to her by him on the previous day. "Ah! non credea mirarti sì presto estinto, o fiore" (Scarcely could I believe it that so soon thou would'st wither, O blossoms).
[[Listen]]
Ah! non credea mirarti sì presto estinto, o fiore,
Gently Elvino replaces the ring upon her finger, and kneels before her. "Viva Amina!" cry the villagers. She awakens. Instead of sorrow, she sees joy all around her, and Elvino, with arms outstretched, waiting to beg her forgiveness and lead her to the altar.