First it's important to determine exactly what a climax does. This is the highest point of action in the story, after which the resolution becomes clear. I would argue that the climax for the play occurs later than act 3, but since your assignment asks you to focus on this act, we'll try to determine where the conflict reaches its highest peak within these scenes.
I would argue that this happens in scene 4, when Banquo's ghost appears and sits in Macbeth's spot at the banquet. Not only does this visibly rattle Macbeth, causing him to talk to a ghost which no one else can see, but Lady Macbeth is forced to begin making excuses for her husband's behavior. When Macbeth's comments intensify, she is forced to dismiss her guests with a sense of urgency.
It is at this point that Macbeth begins to realize that perhaps getting away with murder isn't going to be as easy as he first thought. He turns his suspicions toward Macduff , who failed to appear at the banquet. Macbeth is growing in agitation and...
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