The opera is set in the Lammermoor region of southwestern Scotland, during a time of great political turmoil. The plot centers on the intense feud between two families – the Ravenswoods and the Ashtons. The Ashtons have been triumphant and now occupy Ravenswood Castle. Edgardo, last of the Ravenswoods, has sworn vengeance on the Ashtons, but he and Lucia Ashton have secretly fallen in love. Lucia’s brother Enrico wants her to accept an arranged marriage to Arturo Bucklaw, an important political ally of the Ashtons, but she has refused.

Scene 1. The Grounds outside Ravenswood Castle. Led by Normanno, the Ashtons’ guards search for an intruder. Raimondo, Lucia’s tutor, tells Enrico that her refusal to wed Bucklaw is due to grief over her mother’s recent death. Normanno reveals that Lucia has been having daily rendezvous with Edgardo, whom Enrico promptly vows to murder.

Scene 2. A Fountain within the Castle. Waiting for Edgardo, Lucia tells her maid about hearing a ghostly warning of a tragic end to her romance. Edgardo wants to mend the feud with the Ashtons, but Lucia begs him to keep their love a secret. They exchange rings, vowing to marry when Edgardo returns from a political mission to France.

Scene 1. Enrico’s Study. Enrico forges a letter from Edgardo to Lucia. It tells her that he has fallen in love with another woman. Crushed, Lucia resolves to marry Arturo.

Scene 2. A Great Hall in the Castle. Guests assemble for the wedding. Just as the distraught Lucia signs the marriage contract, Edgardo reappears to claim his betrothed. Seeing Lucia’s signature on the contract, he tears his ring from her hand and curses her. Lucia faints and Enrico vows revenge.

Scene 1. Wolf’s Crag – Edgardo’s Lair. Enrico and Edgardo confront each other and agree to a duel at dawn among the tombs of Ravenswood Castle.

Scene 2. The Great Hall. Raimondo interrupts the wedding festivities with terrible news: Lucia has murdered Arturo in their bridal chamber. She appears, covered with blood and hallucinating that soon she will marry Edgardo. Overcome with madness, Lucia collapses.

Scene 3. The Tombs at Ravenswood Castle. As Edgardo prepares for the duel, he is determined to die, believing Lucia is now married to Bucklaw. From passing mourners, Edgardo learns that Lucia is about to die. Edgardo resolves to join Lucia in heaven and, drawing his dagger, he kills himself.