King Duncan hears how Macbeth has been a brave warrior whilst fighting the Norwegians. Duncan gives Macbeth the title of Cawdor as reward for his valour. the old Thane of Cawdor is sentenced to death for being a traitor.
On their way back from battle, Macbeth and Banquo meet the witches who tell Macbeth that he will become the new Thane of Cawdor and also the new King of Scotland. The weird sisters tell Banquo that his descendants will be the future Kings of Scotland. Macbeth is not sure whether this is true, but a messenger soon tells him that he is now the Thane of Cawdor. This seems, to Macbeth, like the first part of the prophecy has come true.
Macbeth sends a letter to his wife, Lady Macbeth, about the witches predictions. She is excited about becoming queen, but fears that Macbeth is not ambitious enough to kill Duncan. When Macbeth arrives home she tries to persuade him to kill Duncan. Macbeth eventually agrees with her.
Duncan arrives at Macbeth's castle and is greeted by the hosts. They hold a feast and most people get drunk. Macbeth is unsure about killing Duncan and decides to abandon his plan. Macbeth believes that Duncan is a good king and he comments that Duncan has said many good things about Macbeth. Lady Macbeth is angry that Macbeth has abandoned his plan to kill Duncan and calls him a coward. Macbeth decides to go through with the plan to murder Duncan.
Later that night, whilst approaching Duncan's room, Macbeth sees an imaginary dagger before his eyes. He follows the dagger to Duncan's room. Macbeth creeps into Duncan's room and murders him in cold blood. Lady Macbeth sees the daggers in Macbeths's hands and rushes back to plant them on the servents.
Macduff arrives at the castle and discovers Duncan's corpse and raises the alarm. Dunacan's sons, Malcom and Donaldbain quickly leave Scotland because they might be suspected of killing their father. Macduff does not trust Macbeth and suspects that Macbeth might have something to do with it.