Part 1. The Departure
Act I
Scene one. An intruder has been spotted at night on the grounds of Ravenswood Castle. Norman, the captain of the guard, sends his men off in search of the stranger. Lord Henry tells Raymond Bidebent, his sister Lucia’s chaplain and tutor, that his family’s fortunes are in danger. Edgar Ravenswood, the son of the castle’s previous owner, can maneuver Henry out of his property and gain back his political influence. Only the arranged marriage of his sister, Lucia, can save them. However, Lucia does not want to accept the marriage. Raymond reminds Henry that the girl is still mourning the death of her mother. But Norman reveals that Lucia is concealing a great love for a mysterious stranger who saved her from the attack of a raging bull. She meets with him in secret. The returning men reveal the identity of the man whom Lucia is secretly meeting each day – it is Edgar Ravenswood. Henry is furious.

Scene two. Lucia is waiting by an old fountain with her maid Alice for a secret meeting with Edgar. Lucia is frightened by the legend of the fountain: a woman was murdered here by an insanely jealous member of the Ravenswood family. The ghost of the murdered woman has recently appeared to her, beckoning Lucia to follow her. When the ghost disappeared, the water in the fountain turned red with blood.

Edgar appears. He explains that he must leave Scotland and go to France on a political mission. Before he leaves, Edgar wants to ask Henry for Lucia's hand. Terrified of her brother’s reaction, Lucia asks Edgar to keep their love a secret. Edgar tells Lucia of his undying hatred of the Ashtons, how he swore a vow of vengeance upon her family. But now the vow is destroyed by love. The young lovers solemnly pledge their troth by exchanging rings.

Part 2. The Marriage Contract
Act II
Scene one. Guests are arriving at the wedding of Lucia and Lord Arthur Bucklaw. Henry is still worried that Lucia will not accept the groom. Norman reassures him: all the letters that Edgar has written during his long absence have been seized and replaced with artful forgeries in which Edgar confesses that he has fallen in love with another woman. As his sister enters, Henry chastises her for being so melancholy on the day of her wedding. She replies that his cruelty is the cause of her grief. Henry tries to persuade his sister to forget her illicit love and hands her a forged letter. Lucia is shattered: all her tears, her hopes, and her yearning have been wasted on an unfaithful man. At Raymondʼs fervent pleading, the exhausted Lucia finally gives in and agrees to marriage.

Scene two. The guests enthusiastically greet Lord Arthur Bucklaw. Arthur assures Henry of his friendship and promises his support. He asks, however, wherever the rumours about Edgar Ravenswood being in love with Lucia are true. Lucia appears.

Lucia is showed into the room with her marriage contract on the table. There is commotion outside: it is Edgar, who has now returned from France. The men draw their swords. Lucia falls unconscious. Raymond intercedes and shows Edgar the contract with Lucia’s signature. Lucia tearfully confesses that the signature is hers. Enraged, Edgar returns his ring and demands that she returns hers.

Act III
Scene one. A heavy thunderstorm rages outside. Henry visits Edgar at the Wolf's Crag. He challenges Edgar to a duel. They agree to fight in the morning by the graveyard of the Ravenswoods.

Scene two. The guests continue to celebrate the wedding. Raymond breaks up the festivities with terrible news: Lucia has gone mad and stabbed Arthur to death. The crazed Lucia, her nightgown stained with blood, appears in the hall. She thinks that she is once more in the garden, on the way to meet her beloved Edgar. However, her happiness quickly turns into horror as she sees the ghost. Lucia begs Edgar to hide and leads him to the altar decorated with roses. She sees a church, where she is married to Edgar, not Arthur. Lucia collapses.

Scene three. Edgar is at the graveyard of the Ravenswoods, where he is to duel Henry. He laments that he has to live without Lucia and hopes that his duel with Henry will end his own life. Guests coming from the Castle tell him that Lucia has gone mad and is dying. The bell tolls.

Time: Early 18th century
Place: Scotland

Act 1

Scene 1: The gardens of Ravenswood Castle

Normanno, captain of the castle guard, and other retainers are searching for an intruder. He tells Enrico that he believes that the man is Edgardo of Ravenswood, and that he comes to the castle to meet Enrico's sister, Lucia. It is confirmed that Edgardo is indeed the intruder. Enrico reaffirms his hatred for the Ravenswood family and his determination to end the relationship.

Scene 2: By a fountain at the entrance to the park, beside the castle

Lucia waits for Edgardo. In her famous aria "Regnava nel silenzio", Lucia tells her maid Alisa that she has seen the ghost of a girl killed on the very same spot by a jealous Ravenswood ancestor. Alisa tells Lucia that the apparition is a warning and that she must give up her love for Edgardo. Edgardo enters; for political reasons, he must leave immediately for France. He hopes to make his peace with Enrico and marry Lucia. Lucia tells him this is impossible, and instead they take a sworn vow of marriage and exchange rings. Edgardo leaves.

Act 2

Scene 1: Lord Ashton's apartments

Preparations have been made for the imminent wedding of Lucia to Arturo. Enrico worries about whether Lucia will really submit to the wedding. He shows his sister a forged letter seemingly proving that Edgardo has forgotten her and taken a new lover. Enrico leaves Lucia to further persuasion, this time by Raimondo, Lucia's chaplain and tutor, that she should renounce her vow to Edgardo, for the good of the family, and marry Arturo.

Scene 2: A hall in the castle

Arturo arrives for the marriage. Lucia acts strangely, but Enrico explains that this is due to the death of her mother. Arturo signs the marriage contract, followed reluctantly by Lucia. At that point Edgardo suddenly appears in the hall. Raimondo prevents a fight, but he shows Edgardo Lucia's signature on the marriage contract. Edgardo curses her, demanding that they return their rings to each other. He tramples his ring on the ground, before being forced out of the castle.

Act 3

Scene 1: Wolfcrag

Enrico visits Edgardo to challenge him to a duel. He tells him that Lucia is already enjoying her bridal bed. Edgardo agrees to fight him. They will meet later by the graveyard of the Ravenswoods, near the Wolf's Crag.

Scene 2: A Hall

Raimondo interrupts the marriage celebrations to tell the guests that Lucia has gone mad and killed her bridegroom Arturo. Lucia enters. In the aria "Il dolce suono" she imagines being with Edgardo, soon to be happily married. Enrico enters and at first threatens Lucia but later softens when he realizes her condition. Lucia collapses. Raimondo blames Normanno for precipitating the whole tragedy.

Scene 3: The graveyard of the Ravenswood family

Edgardo is resolved to kill himself on Enrico's sword. He learns that Lucia is dying and then Raimondo comes to tell him that she has already died. Edgardo stabs himself with a dagger, hoping to be reunited with Lucia in heaven.