The play opens with the three Witches ("weird sisters") discussing their upcoming meeting with Macbeth. Macbeth, Thane of Glamis, and Banquo, generals to King Duncan of Scotland, have just defeated an invasion of Scotland by the allied forces of Norway and Ireland led by the rebel Macdonwald.
As Macbeth and Banquo wander into a heath the three Witches greet them with prophecies. The first witch hails Macbeth as "Thane of Glamis", the second as "Thane of Cawdor", and the third that he shall "be King hereafter". The Witches also inform Banquo he shall be father of a line of kings. While they wonder at these prophecies, the witches disappear, and the Thane of Ross - a messenger from the King - arrives and informs Macbeth of his new title, Thane of Cawdor--the first prophecy fulfilled (as Macbeth is already Thane of Glamis). Immediately Macbeth begins to harbour ambitions of becoming king.
Macbeth writes to his wife about the witches' prophecies. Duncan decides to stay at Macbeth's castle at Inverness and the couple hatch a plan to murder him and seize the throne. While Macbeth raises concerns about the regicide, Lady Macbeth manages to persuade her husband that murder is the only route to kingship.
In the night Macbeth kills Duncan and the two arrange bloody daggers to frame Duncan's servants for murder. In a sham fit of grief, however, Macbeth murders the servants before they can protest their innocences. Duncan's body is discovered by Macduff, the loyal Thane of Fife, who is immediately suspicious of Macbeth. Fearing for their lives, Duncan's son Malcolm flees to England, and his brother Donalbain to Ireland. Macbeth uses their unexplained disappearances to accuse the pair of regicide. With the rightful heirs gone, Macbeth assumes the throne as new King of...