1. Macbeth meets the witches and they prophesy that he will become Thane of Cawdor and later King of Scotland. This plants a seed of ambition in Macbeth's mind and sets the tragic events of the play in motion.
2. Macbeth murders King Duncan at the urging of his wife Lady Macbeth, fulfilling the first part of the witches' prophecy. This bloody act of regicide draws Macbeth further into tyranny and paranoia.
3. Macbeth begins to feel threatened by Macduff and has Macduff's family murdered. This causes former friend Macdu