Act 1 Scene 3
On the heath the witches appear. They call themselves the "weird sisters" (1.3.30) and brag of their dread and magical deeds such as killing swine and cursing a sailor to waste away.
Macbeth and Banquo enter. The witches hail Macbeth as Thane of Glamis, Thane of Cawdor, and "king hereafter" (1.3.47). Banquo asks Macbeth why he seems to fear this good news, then questions the witches about his own future. They say that Banquo is "lesser than Macbeth and greater" (1.3.63) because though he'll never be king, his descendants will.

At a camp near the battlefield, Malcolm tells Duncan that the old Thane of Cawdor confessed and repented before being executed. Duncan notes that you can't always trust a man by his outward show. Macbeth, Banquo, Ross, and Angus enter. Duncan says that even the gift of Cawdor is not as much as Macbeth deserves. Macbeth responds: "The service and loyalty I owe, in doing it, pays itself" (1.4.22).
Duncan is pleased. He says: "I have begun to plant thee, and will labour to make thee full of growing" (1.4.28-29). Next, he announces that Malcolm will be heir to the Scottish throne (the kingship was not hereditary in Scotland at that time). Duncan then adjourns the meeting and decides to spend the night at Inverness, Macbeth's castle.
Macbeth goes ahead to prepare for the King's visit, but notes that Malcolm now stands between him and the throne. He begs the stars to "hide your fires, let not light see my black and deep desires" (1.4.51).

At Inverness, Lady Macbeth reads a letter in which Macbeth tells her of the witches' prophecy. Lady Macbeth worries Macbeth is too kind and honorable to fulfill his ambition and the prophecy. She decides to question his manhood to make him act.
A servant enters with news that Duncan will spend the night, then exits. Lady Macbeth says Duncan's visit will be fatal, and calls on spirits to "unsex me here… and take my milk for gall" (1.5.39-46).

Duncan, Malcolm, Donalbain, Banquo, Lennox, Macduff, Ross, and Angus arrive at Inverness. Duncan comments on the sweetness of the air. Banquo notes that martlets, a species of bird that usually nests in churches, have nested in the castle.
Lady Macbeth warmly greets the King and the thanes, though Macbeth is nowhere to be seen.

Macbeth, alone, agonizes about whether to kill Duncan. He'd be willing to murder Duncan if he thought that would be the end of it. But he knows that "bloody instructions, being taught, return to plague the inventor" (1.7.10). Also, Macbeth notes, Duncan is a guest, kinsmen, and good king. He decides ambition is not enough to justify the murder.
Macbeth asks what will happen if they fail. Lady Macbeth assures him they won't fail if they have courage. She outlines the plan: she'll give Duncan's bedroom attendants enough wine to ensure they black out from drunkenness. Then she and Macbeth will commit the murder and frame the attendants. Macbeth, impressed by her courage, agrees.

It is after midnight in Inverness. Banquo talks with his son Fleance and notices the stars aren't shining. He prays for angels to "restrain in me the cursed thoughts that nature gives way to in repose" (2.1.7-8).
Macbeth enters. Banquo tells Macbeth his sleep has been troubled by dreams of the weird sisters. Macbeth claims never to think about them. But he suggests they talk about the witches soon, and adds that if Banquo supports him when the time comes he'll reward and honor Banquo for it.
Banquo says he'll be receptive to what Macbeth has to say provided he loses no honor in seeking to gain more. Banquo and Fleance head off to bed.
Alone, Macbeth sees a bloody dagger floating in the air. He can't grasp it, and can't decide whether it's a phantom or his imagination. "Nature seems dead" to him (2.1.50).