Macbeth and Banquo find three witches on the heath. They tell Macbeth that he will be Thane of Cawdor then King of Scotland. They also tell Banquo that will start a line of Scottish kings, although Banquo will never be king himself.
Macbeth becomes Thane of Cawdor and he tells his wife about the witch's prophecy.
Lady Macbeth persuades Macbeth to kill the king so he does and then he becomes king.
Macbeth hires assassins to kill Banquo and his son because the witches said that Banquo's son will become king. However Banquo's son escapes.
Macbeth goes to the witches again and they warn him about Macduff. So he hires assassins to kill Macduff. However, Macduff is in England so the assassins kill Macduff's family.
Macduff and Malcolm raise an army from England. Macduff fights Macbeth and beheads him.