1st act: we can see the failure of the attempt of norway, helped by a traitor, to invade scotland, thanks to macbeth courage. on their way home macbeth and banquo meet three witches. the witches greet macbeth as 'thene of cawdor', noble title that he doen't have yet, and tell him that he will become king of scotland. they also tell banquo that he will father a line of king. so macbeth invites duncan, king of scotland, to his castle and write a letter to informe his wife, who carries out a plan to kill the king