After crushing Macdonwald's rebellion against Duncan, Macbeth and Banquo are journeying to the king's castle when they are surprised by the sudden appearance of three witches. The hags predict that Macbeth, who holds the title of Thane of Glarois, will also become Thane of Cawdor and then king of Scotland and that although Banquo will never rule, his heirs will.