In this summary of Shakespeare's Hamlet:
1) The ghost of Hamlet's father appears to Hamlet and tells him that his uncle Claudius murdered him.
2) Hamlet devises a plan to expose Claudius as a murderer by having a play performed that mirrors the murder.
3) During an argument with his mother, Hamlet mistakes Polonius for Claudius and kills him, believing he is revenging his father's death.
4) Hamlet eventually escapes to stop a pirate ship, but vows to return to Denmark to seek further revenge.