The witches plant desires in Macbeth. Now, he is thinking about becoming king of Scotland. In Act one, Scene four, Duncan mentions that Malcolm will be king; Macbeth comments to himself that this is an obstacle that he will fall on or be hindered by or else he must jump over Malcolm:MACBETH:
[Aside.] The Prince of Cumberland! That is a step(55) On which I must fall down, or else o'erleap, For in my way it lies. Stars, hide your fires; Let not light see my black and deep desires: The eye wink at the hand; yet let that be Which the eye fears, when it is done, to see.(60)
Here, Macbeth mentions that he has "black and deep desires." Macbeth realizes that he should not be desiring to be king. His desires are evil or "black" and way down deep.
Here, the reader can see that Macbeth is having dark, deep thoughts that he should not be having. This is the beginning of his terrible end and downfall.
Duncan is headed to Macbeth's castle, not knowing what evil awaits him.
Lady Macbeth is planning evil. She asks Macbeth how long will Duncan stay. Macbeth claims that he will leave tomorrow. In Act one, Scene five, Lady Macbeth states that Duncan will not see tomorrow:
O, never(65) Shall sun that morrow see! Your face, my Thane, is as a book where men May read strange matters. To beguile the time, Look like the time; bear welcome in your eye, Your hand, your tongue; look like the innocent flower,(70) But be the serpent under't. He that's coming Must be provided for; and you shall put This night's great business into my dispatch, Which shall to all our nights and days to come Give solely sovereign sway and masterdom.(75)
Lady Macbeth plants her evil thoughts in Macbeth. By listening, Macbeth is headed for his downfall.
Macbeth states that they will talk about it further. He is entertaining the thought of murdering King Duncan. He insists that he and Lady Macbeth shall discuss the matter more so:MACBETH:
We will speak further.