The heath — Hecate scolds the witches

The heath. The three witches meet Hecate, the goddess of witchcraft and their queen. She is angry with them. They have been "trafficking with Macbeth in riddles and affairs of death" — and without her involvement. He is, she says, a wayward son: "spiteful and wrathful, who, as others do, loves for his own ends, not for you." She has been excluded from the most important enchantment of their season.

She instructs them. Tomorrow morning, by the pit of Acheron, Macbeth will come to ask his fortune. They are to meet him there. She will go to the moon to gather "a vaporous drop profound" — a magical distillate — and from it she will "raise such artificial sprites" as will, by the strength of their illusion, draw him on to his confusion. The instruction is the play's clearest statement that what the witches will show Macbeth in the next act is designed to deceive. They will show him "such things as may seem to spurn fate, scorn death, and bear his hopes 'bove wisdom, grace, and fear." Security, Hecate says, is mortals' chiefest enemy. The plan is to make Macbeth feel safe and act on the feeling.

The scene is short — about forty lines — and is widely thought to be a later addition, possibly by Thomas Middleton, partly because the verse is strikingly different from Shakespeare's witches elsewhere and partly because it is loosely connected to the play's main movement. It has nonetheless remained in the standard text since the First Folio. What it does, dramatically, is name in advance what Macbeth's overconfidence in the next act will mean. He will be lulled. He will believe he cannot be killed. The belief will get him killed. The play is showing the audience the trap before it shows Macbeth walking into it.