The noble families Ravenswood and Ashton have been enemies for as long as anyone can remember. The last Ravenswood, Edgardo, has sworn bloody revenge on Enrico Ashton, whom he blames for the death of his father and the loss of the family estate. Now, however, the Ashtons have gotten themselves into trouble. Enrico sees only one way to preserve political power and wealth for his family and to save the Ashton dynasty from its demise: his sister Lucia must marry Lord Arturo Bucklaw. However, Lucia herself does not want to know anything about this. She fell in love with Edgardo of all people after he saved her life when a wild bull attacked her. Before Edgardo, who reciprocates Lucia's love, embarks on a journey abroad, the two promise each other eternal loyalty. Lucia's persistent refusal to marry Arturo puts Enrico in distress. He therefore instructs Normanno to intercept the letters that Lucia and Edgardo are writing to each other and to forge a document alleging Edgardo's infidelity. Lucia is dismayed by this letter. But only when her tutor Raimondo urges her to agree for the sake of the family and convinces her that the vow of allegiance to Edgardo is invalid anyway - because it was not confirmed by a priest - does she resignedly agree to her marriage to Arturo. Shortly after she has signed the marriage contract, Edgardo returns, surprising everyone. To him, Lucia's signature is such proof of her infidelity that he curses Lucia and the entire Ashton family. Lucia collapses. In order to finally destroy his mortal enemy, Enrico visits Edgardo that same evening and challenges him to a duel for the next morning. Lucia kills Arturo on their wedding night and hallucinates the happy union with her lover Edgardo. Her shattered spirit drains her vitality. When Edgardo learns of Lucia's madness and hears her death knell ring, he ends his life.