Macbeth Act 1, Scene 4
At the palace at Forres Duncan hears of Cawdor's execution. Cawdor died without begging for mercy, and Duncan is shocked by his own misplaced trust. Such a deep betrayal makes him feel foolish. Macbeth and Banquo then arrive at the palace. Duncan thanks Macbeth for his loyalty and tells him that there is no way to repay him for his service.
Duncan then announces that his son, Malcolm, is to be the Prince of Cumberland and heir to the Scottish throne. Macbeth at once sees that Malcolm is blocking his path to the throne and preventing the witches' prophecy from coming true. Macbeth begins to desire the Scottish throne and realizes that in order to get it he will have to be devious. He leaves ahead of the other lords and the king in order to prepare his castle for Duncan's arrival.