On a barren heath in medieval Scotland, three groups of witches gather to exchange news. Two Generals, Macbeth and Banquo, appear and greet the witches, who hail Macbeth as Thane of Glamis, Thane of Cawdor, and King of Scotland, adding that Banquo will sire a race of kings. The witches suddenly vanish, leaving the two men perplexed. Messengers arrive with word that the king has awarded to Macbeth the title Thane of Cawdor, fulfilling the witches’ prediction. After the men leave, the witches return briefly, agreeing to meet again later.
In Macbeth’s castle, Lady Macbeth reads a letter from her husband telling of the meeting with the witches. She pledges herself to spur his ambition for the throne (Vieni! t’affretta!). When a servant announces that King Duncan is to arrive that very night with Macbeth, she calls on the ministers of hell to aid her plan (Or tutti sorgete). Macbeth enters, and she tells him they must strike that night. Duncan arrives, accompanied by his attendants, and is shown to his room by Lady Macbeth. Macbeth sees a vision of a dagger before him (Mi si affaccia un pugnal?). Signaled by the night bell, he goes to perform the murder; on his return, he finds his wife waiting. He tells how unnerved he is by his act, while she retorts that he needs greater courage (Fatal mia donna!). She takes the dagger herself to smear Duncan’s sleeping guards with blood and make them seem the murderers. A knock at the castle gate terrifies the guilty Macbeth. Lady Macbeth returns, and they both withdraw as Macduff and Banquo enter. Macduff goes to waken the king and discovers the murder, rousing everyone in the castle. Macbeth and Lady Macbeth hypocritically join in the common expression of horror and shock (ensemble: Schiudi, inferno),
Macbeth has been named king, thanks to the flight to England of Duncan’s son, Malcolm, who is assumed to have plotted the murder of his father. Worried about the prophecy that Banquo’s heirs will rule, Macbeth now plots with his wife to do away that very night with Banquo and his son, Fleance. As Macbeth goes to arrange the deed, Lady Macbeth welcomes the approaching darkness (La luce langue).
In a park outside the castle, assassins gather to carry out Macbeth’s orders; they too welcome the darkness to cover their deed (Sparve il sol). They hide as Banquo approaches, who warns his son of strange forebodings (Come dal ciel precipita). The assassins emerge to murder him, but his son, Fleance, escapes.
A great state dinner is being held and in the banquet hall and Lady Macbeth welcomes the court, offering a drinking song (Si colmi il calice). Aside, Macbeth receives word that Banquo is dead but that Fleance has escaped. Turning to the guests, Macbeth says that he regrets Banquo’s absence and moves to take his seat—only to find it occupied by the ghost of the dead man. The other nobles inquire about what is wrong with Macbeth, as his wife makes excuses, saying he is sometimes prey to seizures. She tries to resume the drinking song, but soon afterward Macbeth again sees Banquo’s ghost, crying out that he must revisit the witches (Sangue a me). Macduff privately vows to leave the country, which, he mutters, is now ruled by murderers, as the courtiers wonder at the cause of Macbeth’s strange behavior.
In a cave on the heath, the witches add infernal ingredients to their cauldron, invoking the powers of darkness. Macbeth enters their lair, demanding more prophecies. They conjure up a warrior’s head, which warns Macbeth to beware of Macduff. Next they conjure the vision of a bloody child tells him “no man of woman born” can harm him; then a crowned child carrying a bough, who says Macbeth will be invincible “till Birnam Wood shall come to Dunsinane.” Macbeth insists on knowing whether Banquo’s heirs will rule. A procession of eight future kings is seen, followed by Banquo holding a mirror. When Macbeth swoons at the sight, the witches summon Hecate and spirits of the air to revive him. Then they disappear, leaving him on the heath. He repeats the prophecies, and resolves to kill Macduff and his family as well as Banquo’s son (Ora di morte e di vendetta).
Macbeth has killed Macduff’s wife and children, while near Birnam Wood and the English border, refugees bemoan Scotland’s fate. Macduff laments the reported slaughter of his wife and children, wishing he had been there to defend them (Ah, la paterna mano). Malcolm appears at the head of British forces, and all pledge to overthrow the tyrant (La patria tradita).
In Macbeth’s castle, a physician and lady-in-waiting watch for the appearance of Lady Macbeth, who nightly enters sleepwalking, reliving the murders and muttering that there is still blood on her hands (Una macchia) that all the perfumes of Arabia cannot cleanse or sweeten.
Alone, Macbeth prepares to meet his foes, knowing he will never live to enjoy a peaceful old age (Pieta, rispetto, amore). Servants rush in to tell him that Lady Macbeth has died and that, amazingly, Birnam Wood appears to be moving toward the castle. He grabs his arms and summons his followers. Noises of combat are heard, and soldiers led by Malcolm appear, having camouflaged themselves with tree branches. Macduff confronts Macbeth, who scorns him saying that “no man of woman born” can harm him, whereupon Macduff announces he had a Caesarean birth and was “untimely ripped from his mother’s womb.” The two men fight, and the dying Macbeth falls to the ground cursing the day he met the witches (Mal per me). Malcolm leads in their soldiers to meet Macduff who brandishes the head of Macbeth. All rejoice in the usurper’s death and the liberation of their land, hailing Malcolm as rightful king (S’affidi ognun al Re).