ACT I
For political reasons Lord Henry Ashton has arranged the marriage of his sister Lucia to Lord Arthur Bucklaw. Lucia, however, refuses this match. Norman, Ashton’s huntmaster, reveals that the young girl is in fact in love with Edgar of Ravenswood, the members of whose clan are old rivals of the Lammermoors. Ashton decides to use all the means at his disposal to put an end to this love. Lucia awaits Edgar’s arrival. She evokes the tragic fate of a woman killed in the distant past by her jealous lover, a Ravenswood. In a dream she saw the ghost of the luckless victim who seemed to call out to her. In spite of her maid Alisa’s gloomy premonitions, she sings of her love for the young man and her faith in the future. Edgar has to leave for France for a time. Before his departure, he wishes to ask Ashton for Lucia’s hand but, fearing her brother’s reaction, she dissuades him. Edgar and Lucia exchange rings and swear to be faithful to each other.

ACT II
Taking advantage of the young man’s absence, Ashton manages to convince his sister of her lover’s infidelity. Raymond, the chaplain, assures the young girl that it is her duty to sacrifice herself for the good of her family. In despair Lucia agrees to marry Arthur, the suitor chosen by her brother. No sooner has she signed the marriage contract than Edgar appears. In a celebrated sextet all the characters express their feelings in the light of the unexpected turn of events. Convinced of the betrayal of the woman he loves, Edgar curses her publicly. Lucia feels her reason begin to waver.

ACT III
In a raging storm Ashton comes to Edgar’s home to challenge him to a duel, taunting him with the reminder that Lucia now belongs to another. They agree to fight at dawn near the tombs of the Ravenswoods. The wedding festivities are interrupted by Raymond who announces that Lucia, in a fit of madness, has killed her husband. She appears and, in her madness, believes she has married Edgar.This is the famous mad scene, at the end of which the young woman collapses, unconscious. Unaware of the drama, Edgar awaits his adversary. He does not care if he dies, for he cannot live without Lucia. His melancholy monologue is interrupted by the arrival of Raymond, who tells him of the death of his beloved. He stabs himself.