In Act I of 'Hamlet,' a ghost resembling the late King Hamlet reveals to his son Hamlet that he was murdered by his brother Claudius, who has taken the throne and married Queen Gertrude. Throughout the play, Hamlet grapples with revenge, morality, and the nature of existence, leading to tragic outcomes including the madness and drowning of Ophelia, the death of Polonius at Hamlets hands, and a fatal duel with Laertes. The play concludes with Hamlet's death and the passing of the crown to Fortinbras, as he urges Horatio to tell his story.