The supernatural atmosphere of scene one is recreated by the witches' description of their evil doings and by their charm. Their power is limited; they cannot kill the sailor but they can make his ship meet terrifying storms, and the poor man's life a hell on earth. This foreshadows the outcome of the witches' influence on Macbeth. He too will, for example, deprived of sleep. The limitation of their powers is an important fact to keep in mind.
Macbeth's first words echo those of the witches in scene 1, and link him to these evil beings. Macbeth, despite his valour and apparent loyalty to the king, must have some guilty secret. The witches want to speak to him - Banquo just happens to be with him. Would the witches have any dealings with people who are totally innocent? Do they have enough power to corrupt good people or can they only act on the evil already present in them? Apparently, the latter is the case. Notice the different reactions of Macbeth and Banquo to the hags' prophecies. The former is profoundly disturbed ('he seems rapt withal' line 57) The witches foretell Macbeth's future but make no mention of regicide; it is Macbeth who immediately thinks of resorting to murder. This and his reaction ('Good Sir, why do you start, and seem to/ fear/ Things that do sound so fair?' Lines 51 - 53) suggest that the thought of usurping the throne by killing the old and frail King Duncan has already crossed his mind.