The actual murder is carried out off-stage. This is because Shakespeare is forcing us to use our imagination. He can use images to make the murder much more horrible and dramatic than would be possible if we watched an actor pretending to kill another actor.

Macbeth appears and announces that 'I have done the deed'. The alliteration of the letter 'd' gives a sense of finality to what he has done. Look at how each speaks in short bursts rather than in long, fluent sentences:

Macbeth: 'When?'

Lady Macbeth: 'Now.'

Macbeth: 'As I descended?'

Lady Macbeth: 'Ay.'

Macbeth: 'Hark! Who lies i'th' second chamber?'

They are nervous and uncertain about what they have done. Macbeth is mesmerised by the terrible nature of his deed. He wants to feel some sort of forgiveness or absolution from God:

'But wherefore could I not pronounce 'Amen'?

I had most need of blessing, and 'Amen'

Stuck in my throat.'

We learn earlier in the play that Duncan was a holy man, and one of the reasons Macbeth had at first hesitated to kill him was that he would be condemned for carrying out such an evil deed. The truth of this is already hitting him. Shakespeare uses a striking metaphor to sum up what the consequences will be:

'Macbeth does murther Sleep!'

This becomes increasingly true as the play progresses. Lady Macbeth finds herself literally unable to sleep and we see her sleepwalking into suicide. Macbeth, too, cannot find peace or rest. He finds himself being driven to commit more and more horrors in order to secure his position as king. He never finds the peace he seeks.

It is Lady Macbeth who is still in control in this part of the play. Macbeth has not carried out the plot as he should have done. He was supposed to wipe the daggers of Duncan's two grooms (bodyguards) with the king's blood to make it seem as if they were guilty of the murder. He forgot to do this, and it is Lady Macbeth who summons up the strength to go back into the king's chamber and do this. It is she who issues the orders:

'Go, get some water,

And wash this filthy witness from your hand.'

Again, there is a dramatic irony here. Later in the play, it is she who shows her guilt by trying to wash blood from her hands while sleepwalking. She is all action now, but she keeps the guilt inside her only for it to appear again later.

Imagine this scene on stage. It is the middle of the night. It is dark. There is evil lurking in the air. And then Shakespeare increases the tension still further with the sound of knocking. Macbeth jumps:

'Whence is that knocking?

How is't with me, when every noise appals me?'

The knocking continues until the end of the scene. It is like the thumping of Macbeth's heart or conscience. It leads into the next scene when the porter opens the gate.

The porter is a down-to-earth, common character who talks in ordinary, coarse language. It is Shakespeare's way of diffusing the enormous tension that was built up in the preceding scene. It also gives a pause for the audience to think about what has happened. But Shakespeare raises the tempo again, as we wait to see what will happen when the murder is discovered.

It is like a roller-coaster ride as the tension ebbs and flows.