Summary
Lady macbeth wants to speak to her husband before the feast, she is on edge and uncertainty and insecurity trouble them both.Macbeth appears and she scolds him both for staying alone and for his continued dwelling on their actions.

They discuss the feast ahead, resolve to praise Banquo at it, and then Macbeth reveals his fear of banquo and fleance. He reveals that he intends to commit another dreadful crime, he will not tell lady macbeth what it is, but asks her to praise it when it is achieved.

Why is this scene important?
We see macbeth growing in evil, and hardening himself to commit more crimes.Duncan's peace of mind, being dead, is now a source of envy to macbeth, who is in torment and has had dreadful nightmares.Lady Macbeth is no longer controlling and driving the action of her husband, but trying to calm his troubled mind.

The initial hope that they would enjoy their reign together is now exposed as hollow.

Who is the key character in this scene?
Macbeth The third act marks the turning point for our tragic hero. In the first part of the play we have seen macbeth rise to power. Now he is king, he is hardening and becoming more brutal, and shakespeare shows the situation changing. Macbeth keeps himself to himself and broods on the crimes committed, and on the crimes he intends to commit, shakespeare uses dark imagery ' O, full of scorpions is my mind'. Just as scorpions bring death, so does the tormented macbeth.

He no longer shares his thoughts with his wife so she feels isolated. The affectionate term, 'dearest chuck' that macbeth uses for her seems to imply a shift in power.For lady macbeth this scene marks the start of her breakdown, she will take control one more time, at the banquet, after which she will be overwhelmed by remorse for the tide of evil she has helped unleash. Their roles are reversing.