The action takes place in Scotland towards the end of the 17th century. Lord Enrico of Lammermoor Castle is perpetuating a family feud with the Ravenswood clan. Edgardo the young lord of Ravenswood, whose father was killed and whose estate usurped by Enrico’s father, is now a fugitive.

Act 1

Scene 1: The grounds of Ravenswood Castle

On the grounds near Ravenswood Castle, Normanno, the chief huntsman of Enrico, urges his men to seek out the stranger who has lately been lurking about. Enrico, entering with Raimondo, the chaplain, is preoccupied with his declining fortunes and upset that his sister Lucia refuses to marry the one man who can prevent his ruin. Raimondo suggests that Lucia is still mourning her recently deceased mother; but Normanno declares that she is in love with the intruder being hunted down, whom he suspects to be Edgardo. Enrico vents his anger in the aria. The huntsmen return and report definite identification of the stranger as Edgardo, news that arouses Enrico to another outburst.

Scene 2: By a fountain in a park near Ravenswood Castle

In the park of Ravenswood Castle, Lucia with her companion Alisa awaits Edgardo by the haunted fountain. She tells Alisa the legend of the victim of a passion killing who haunts the fountain, whose ghost has recently appeared to her. Alisa sees this as a dire omen and warns Lucia, who remains convinced of Edgardo’s sincerity. Edgardo enters and bids Lucia farewell, as he must leave that night on a political errand to France. Edgardo is determined to ask Enrico for Lucia’s hand before he departs, but finally yields to Lucia’s dissuasion. They solemnly exchange rings, pledge their mutual faithfulness in the love duet and separate in anguish.

Act 2

Scene 1: Enrico Ashton’s chamber

In the Castle of Lammermoor, Enrico, who has intercepted the correspondence between Lucia and Edgardo, now forges a letter proving Edgardo’s infidelity with Normanno’s help. Lucia enters, reproaching her brother’s harshness. Enrico produces the forged letter and Lucia is grief-stricken. Enrico enjoins Lucia to marry Arturo, his only hope of salvation, threatening that if Lucia should betray him, the executioners’ axe awaits him and his ghost will haunt her.

Scene 2: The wedding reception hall

In the great hall of Lammermoor Castle, Enrico leads in Arturo, followed by the guests for the betrothal. Arturo asks about the rumour that Edgardo had courted Lucia, but Enrico’s efforts to brush this aside are interrupted by the arrival of Lucia. The marriage contract is signed with Lucia barely aware of what she is doing. Edgardo bursts in to claim his bride. In the famous Sextet, everyone reacts to this sudden intrusion. Raimondo steps between the drawn swords, bidding them remember God’s law against murder, and shows Edgardo the marriage contract. The furious Edgardo gives Lucia back her ring, snatches his from her and tramples it as he curses her. The act closes with a headlong ensemble.

Act 3

Scene 1: The great hall of Lammermoor Castle

The wedding guests continue rejoicing in the great hall. Raimondo enters with the shocking news that Lucia, apparently out of her mind, has stabbed Arturo to death in the wedding chamber. The gathering hope that this dreadful deed will not call down upon them the punishment of heaven. Lucia appears, imagining in her madness that she has been happily united with Edgardo, and conjuring up a vision of the nuptial altar. Enrico arrives and is filled with remorse at this tragic sight. Lucia declares that heaven will be empty for her until she is joined there by Edgardo as she falls dying into Alisa’s arms.

Scene 2: The Ravenswood graveyard

Edgardo, musing among the tombs of the Ravenswoods, declares he has no desire to live without Lucia, and longs to die on Enrico’s sword so as to join his ancestors. News comes that Lucia is dying, and Edgardo is frantic with grief when he hears the death-bells tolling. Raimondo enters to confirm Lucia is really dead. Edgardo prays for reunion with Lucia in heaven and stabs himself.