The three witches meet upon the heath and come up with a plan to mess with peoples lives
The witches tell Macbeth that he will be made thane of Cawdor and will eventually become kind. They also tell Banqou although he will never be king, his descendants will.
Almost immediately, Macbeth receives the news that in gratitude for leading his troops to victory Duncan is making him Thane of Cawdor. Lady Macbeth encourages her husband to kill Duncan to take the throne.
Macbeth and his wife plan and carry out Duncan's murder. When Macbeth hesitates, his wife encourages him; and he kills king Duncan
They try to cover up their deed by making it seem as if the King's servants are responsible
Malcolm and Donalbain, the king's sons, flee the country and the way is left clear for Macbeth to seize the throne.