Scotland, 17th century. Lucia and Edgardo love each other in secret: their families have been enemies for generations. Edgardo must leave for France. They exchange vows of marriage. Enrico, Lucia's brother, needs a political alliance and has already chosen another husband for her: Arturo Bucklaw.

Enrico convinces Lucia that Edgardo has abandoned her by showing her a forged letter. Lucia, broken, signs the marriage contract. At that very moment Edgardo bursts in, returned from France. He sees the signature. He curses her. Lucia cannot explain herself. The quartet that follows — Lucia, Edgardo, Enrico and Raimondo — is one of the most heartbreaking moments in all bel canto history.

That same night, during the wedding feast, Raimondo comes down the stairs with a stricken face. Lucia has killed her husband in the bridal chamber. Then she appears — in a white wedding gown stained with blood, eyes unseeing. She sings in another voice, from another life. She is already elsewhere. She dies shortly after. Edgardo, on hearing the news, stabs himself on the Ravenswood tomb.