ACT I
In the Capuleti palace.
The Capuleti leader, Capellio, informs his supporters that Romeo, leader of the Montecchi, is sending an ambassador to propose peace  between the two enemy factions. Despite Lorenzo’s advice, Capellio refuses any negotiation because Romeo has killed his son. Tebaldo swears to avenge him and urges Capellio to hasten his marriage to Giulietta. The ambassador arrives: it is Romeo, incognito. He proposes that Giulietta (with whom he is secretly in love) marry Romeo to seal the reconciliation between the two families. Faced with Capellio’s inflexibility, he realises that conflict is inevitable.
In Giulietta’s bedroom.
Giulietta has learned that she is to marry Tebaldo on the same day. She despairs because she is in love with Romeo. Lorenzo ushers Romeo in through a secret passage. Romeo pleads in vain with Giulietta to elope with him; she refuses, citing honour and filial love. The arrival of Capellio forces the young man to flee.
In the Capuleti palace.
The wedding between Giulietta and Tebaldo is about to take place. Disguised, Romeo joins the guests, determined to do anything to prevent the union. His supporters have secretly entered the city and a battle breaks out between the two clans. Giulietta is torn between her love and her concern for her family. Romeo once again comes to beg her to flee with him. They are surprised by Capellio and Tebaldo. Unmasked, Romeo is saved only by the arrival of his friends.

ACT II
In the Capuleti palace.
Lorenzo reassures Giulietta about Romeo’s fate: he has escaped unscathed from the battle that followed the aborted wedding. But Capellio has not given up. Lorenzo offers Giulietta a final means of escaping the marriage: to drink a potion that will plunge her into a deep sleep that will look like death. She is taken to the family vault, where he and Romeo will await her awakening. At first frightened, the young woman accepts this ploy. Capellio once again orders his daughter to marry Tebaldo. Giulietta begs her father’s forgiveness and returns falteringly to her room. Capellio orders that Lorenzo, whom he distrusts, be put under close surveillance.
Outside the Capuleti palace.
Romeo searches for Lorenzo. Surprised by Tebaldo, who recognises him, he is about to fight a duel when a chorus of lamentations interrupts them. A funeral procession mourns Giulietta’s death. The two men, devastated, stop fighting.
In the Capuleti vault.
Romeo enters the vault and asks his friends to leave him alone for a moment. He takes poison. Giulietta slowly wakes from her lethargy, glad to see her lover at her side. Romeo, aghast, realises his mistake. Despite Giulietta’s pleas, he dies in her arms. The young girl collapses over his body, while the Capuleti and Montecchi enter and accuse each other of the death of the two lovers.