Returning triumphant from battle, Macbeth and Banquo encounter three witches on a heath, who predict that Macbeth shall be Thane of Cawdor, and subsequently king of Scotland, and that Banquo shall be a father of kings. Soon Macbeth hears that he has been made Thane of Cawdor. Spurred on by the prophecy and by his ambitious wife Lady Macbeth, Macbeth murders King Duncan, who is visiting his castle at Dunsinane. Duncan's sons Malcolm and Donalbain flee in terror, and Macbeth is crowned king.
Macbeth has Banquo killed, but Banquo's son Fleance escapes. Macbeth revisits the witches and is told that he should beware Macduff, that he can be harmed by no man born of woman, and that he is safe until Birnam Wood comes to Dunsinane. Macbeth has Macduff's wife and children killed, while his own wife goes mad and dies. Malcolm brings an army to attack Dunsinane, using leaves from Birnam Wood as camouflage, and Macduff, who was not born but cut from his mother's body, kills Macbeth. Malcolm is proclaimed king.
—Summary taken from The World of Shakespeare.