Scotland in the near-future.
In a feud between the Scottish families of Ravenswood and Lammermoor, Enrico Ashton of Lammermoor wrongfully holds the estates of Edgardo Ravenswood. In addition, Enrico’s political activity against the king has placed him in a perilous situation, and he has resolved to reestablish his family’s position by marrying his sister Lucia to Lord Arturo Bucklaw.
Normanno orders his henchmen to discover the identity of the man whom Lucia is secretly meeting each day before dawn. Enrico is frustrated because he cannot persuade his sister to accept a marriage that will save him politically, and Normanno tells him his suspicions concerning Lucia’s lover. Enrico’s outburst is interrupted by the return of his men confirming that Lucia’s lover is in fact his enemy Edgardo.
Lucia awaits Edgardo in the woods by a fountain whose legend of a bloody phantom alternately fascinates and repels her. Edgardo arrives with the news that he must leave for France. He tells Lucia that before departing he wishes to ask Enrico for her hand in marriage. Terrified of her brother’s reaction, Lucia begs him not to. She tries to calm him when he renews his vows of vengeance upon her family. They solemnly pledge their troth by exchanging rings and vows of eternal fidelity, promising to write during their separation.
In his fury at his sister’s betrayal, Enrico has concluded marriage preparations for the union of his sister with Arturo. Despite his insistence, Enrico has failed to secure Lucia’s consent to this arranged marriage. Lucia remains obstinate even when presented with a letter, forged in Edgardo’s handwriting, announcing his marriage to another woman. Enrico explodes in rage against his sister. At Raimondo’s fervent pleading, the exhausted Lucia finally gives in.
The wedding party has assembled and Lucia has scarcely signed the marriage contract when Edgardo bursts into the castle demanding an explanation. Upon seeing the contract with Lucia’s signature, he curses her and her family forever. Enrico finally places his sister’s hand in Arturo’s.
In a tower of Edgardo’s gloomy castle, Enrico arrives at night to challenge him to a duel the next morning. The wedding celebration is in progress when Raimondo brings the terrible news that Lucia has slain her bridegroom and has gone mad. In her delirium, Lucia wanders into the hall and imagines a wedding ceremony with her beloved Edgardo.
Enrico returns and finds his sister insane. He suffers remorse as she loses all reason while begging Edgardo to pray at her tomb. Unaware of all that has happened, Edgardo imagines Lucia’s happiness with Arturo and berates her for her infidelity. A party of mourners leaving the castle brings word of Lucia’s misfortune. As Edgardo sets off to see her one last time, Raimondo stops him with the news of Lucia’s death. In his grief, Edgardo stabs himself with the hopes of being reunited with Lucia in heaven.