A son avenges his father's murder, but his madness and indecision take its toll on everyone.
The general idea behind the play is what Hamlet learns in Act V which is to renounce his hubris and conform to the "divinity that shapes our ends,/Rough hew them how we will."
I love this thread's question! Hamlet is not really about the fall of the house of Denmark or Ghosts or Norwegian princes. Hamlet is about Life's dissapointment. Its about stripping away layer after layer of false meaning and experience and finding all of life's absurdities. But then finding they won't fit back together again and that life still goes on, however damaged and absurd it all is.
Hamlet is Shakespeare's rant at the world. It is one long existential scream. In the 20th century, Philosophy shrugged it's shoulders and concluded, "Basically; life is absurd, and there's nothing we can do about it."
Hamlet's journey is the discovery and acceptance of this.
Life; an advanced user's guide.
Hamlet seeks the objective truth of his new situation, believing he has been wrongly overturned from being the Prince/heir to the throne,though his apprehensions puts him in a treasonous position, he perseveres craftily, even after having moral proof, to obtain general objective evidence, in the last scene when Laertes states the King is responsible, even after an interlude when the court, calling 'Treason' , does not make it clear if they mean Hamlet's stabbing of Claudius with the poisoned foil, or Claudius' preparing both it and the poisoned cup which kills Gertrude. At his death, he is vindicated, but he knew the game was very dangerous.
The general idea of Hamlet is to get rid of deep shocks by taking avenge of his father from his serpent uncle who is murderer and a wolf in sheep clothes.
The general idea of Hamlet is to take revenge of his father`s death from his uncle and to prove himself a prestigous son.