A main theme of Macbeth is that the characters experience paranoia when they have committed a sinful action. An obvious example of this is when Macbeth witnesses Banquo's ghost right after learning that his plan to kill Banquo was a success. When he first sees the ghost, he says, "You can't say I did it." Don't you ever shake your bloody locks at me. » (3.4.61-2) These lines show Macbeth's paranoia about Banquo's death. When he says these lines he is in a room full of people and seems pretty crazy because they think he is talking to himself or seeing things, which is actually the case. This example shows that Macbeth is so paranoid that he imagines things in his head. This shows that he is terrified of what would happen if the truth came out.