Scene 1. On the grounds of Ravenswood Castle: Normanno orders his men to find a mysterious intruder who is hidden somewhere on the estate. Enrico cannot understand why his sister Lucia refuses to accept a marriage that will restore the family’s fortune, but Normanno tells him he suspects Lucia has a secret lover and that lover is Edgardo, Enrico’s mortal enemy. The men return, confirming that the intruder on the estate is indeed Edgardo.

Scene 2. A park on the Castle grounds at Lammermoor: Lucia awaits Edgardo by a fountain where she once saw the bloody ghost of a murdered young woman — when the ghost vanished, the waters of the fountain had turned red with blood. Edgardo tells Lucia he must leave immediately for France. The two lovers solemnly pledge their troth by exchanging rings and vowing their eternal love for each other.

Scene 3. Enrico’s apartment in Lammermoor Castle: Enrico tries desperately to convince Lucia of the importance of her marriage to Arturo. Lucia remains true to her vows to Edgardo, even when her brother shows her a letter, forged in Edgardo’s handwriting, telling of his love for another woman. Enrico threatens Lucia that if she does not marry Arturo, this will rob him of his life and he will return to haunt her for the rest of her life. Raimondo, the priest, tells Lucia that if she does not relent, her dead mother will shudder in her grave.

Scene 4. The great hall of Ravenswood Castle: The wedding party has assembled and Lucia has scarcely signed the marriage contract when Edgardo bursts in. For a moment, everything seems to stand still as each of the charac[1]ters tries to understand the horror of what is happening to them. Upon seeing the contract with Lucia’s signature, Edgardo realizes that Lucia has broken her sacred vows and he demands the return of his ring.

Scene 1. A room in the tower at Wolf’s Crag: Galloping through the terrible storm, Enrico comes to challenge Edgardo to a duel. The two men agree to fight to the death in the morning.

Scene 2. The great hall of Ravenswood Castle: With Arturo and Lucia’s wedding, the family’s fortune has been saved and a wild celebration is in progress when Raimondo bursts in: Lucia has murdered her new husband in their wed[1]ding chamber and she has gone insane. In her madness, yet infinitely happy at last, Lucia imagines she is marrying her beloved Edgardo.

Scene 3. Outside the Castle at Wolf’s Crag: As he waits for Enrico to arrive in order to fight their duel, Edgardo imagines how happy Lucia must be in Arturo’s arms. A party of mourners brings word of Lucia’s madness and as the bell tolls, Raimondo tells Edgardo of Lucia’s death. Unable to bear the thought of life without his beloved, Edgardo kills himself.