Be careful how you treat people...What you do to others has a funny way of coming back on you. May want to sleep with one eye open. That is one crazy piece of work you have there! I'm willing to bet you know that already!!
After Hamlet learns about his father's murder it drives him insane. Hamlet has seen the spirt of his father. Now he wants to get revenge on his uncle. He's seeking revenge because it was his uncle who poisened Hamlets father. Now the spirt of Hamlet's dad tells Hamlet this is what he wants him to do.