Act 3 is the centre of most Shakespearean plays. By Act 3 of
Macbeth, Macbeth has succeeded in becoming the king as he had
hoped. He is still uneasy about his situation, and hopes to cure
his uneasiness by irrational violence. The first such act is to
assassinate Banquo, but it results in Macbeth becoming increasingly
unstable, even in public, and particularly at the dinner party
where he sees Banquo's ghost.