Ever since Duncan's death, Lady Macbeth's conscience has been troubling her. She has taken to sleepwalking and tries to wash her hands clean of imaginary blood. She eventually dies; it is suggested by Malcolm later that she kills herself, but Macbeth seems almost too preoccupied to notice.
Malcolm and Macduff's invasion begins; Macbeth still thinks he is protected by the Witches' predictions but he is wrong. When the invading army cut down the trees in Birnam Wood to use as camouflage, as they move to Macbeth's castle in Dunsinane, it seems as though the trees themselves are moving.
Macduff comes face-to-face with Macbeth in battle. Macbeth boasts that Macduff cannot harm him but Macduff declares that he was not born naturally (but by Caesarean section). The two men fight and Macduff kills and then beheads Macbeth. Malcolm is declared the new king of Scotland.