Act I scene i of Macbeth is a very short scene and only the three witches are present. The audience is introduced to an ominous apparition and inclined to wonder, at this early stage, what is to follow. The scene then foreshadows what is likely to happen when "fair is foul and foul is fair."(I.i.10) Superstition was prominent in Shakespeare's day and the audience would have known that all will definitely not be as it seems and that the witches can only mean trouble. The witches say very little but it is the setting and the mention of Macbeth's name that prepares the audience. If the witches expect disorder, then there will most certainly be disorder. The balance of nature is upset and this is reinforced by the approaching storm.
Shakespeare creates the visual images and the drama through the witches. The concept of the disturbed mind is evident as the witches expect the battle to be over soon, when it's "lost and won"(4) and the fact that it is Macbeth that they will meet on "the heath" is enough information to show that, in meeting with a noble, valiant soldier, someone is plotting something.