In his first encounter with the witches, Macbeth is at first dubious about what they say. He has stumbled upon the witches while returning from battle with Banquo, and the witches have things to say that are of interest to both men. Macbeth is disturbed but intrigued by their prophecies, leading Banquo to ask:
Good sir, why do you start, and seem to fear
Things that do sound so fair?
By Act Four, much has happened. Macbeth has murdered Duncan and had Banquo murdered. Indeed, the appearance of his old friend's ghost at a banquet is the reason Macbeth seeks out the witches. This time, he beseeches them for predictions on his future, and he is willing to believe the spirits they sumon without question, mostly because they tell him things he wants to hear. He is angered, however, when they summon an image of Banquo followed by a line of kings.