King Hamlet appears as a ghost, telling Hamlet the truth behind his death.
Hamlet has to figure out if this ghost is telling the truth. If this is his father, he may have cracked the case. If not, there could be major reprecussions if he acts too soon. `
During the play, the actor is about to kill the king via poisoning him in his ear. At this moment, Claudius calls for the lights to come on. Hamlet now knows the truth about his father's death.
He won't be alive for much longer!
“I am thy father's spirit, Doom'd for a certain term to walk the night, And for the day confined to fast in fires, Till the foul crimes done in my days of nature, Are burnt and purged away.” Shakespeare 1.5.72
“The spirit that I have seen May be a devil, and the devil hath power T' assume a pleasing shape, yea, and perhaps Out of my weakness and my melancholy, As he is very potent with such spirits, Abuses me to damn me. I'll have grounds More relative than thin I'll catch the conscience of the King.” Shakespeare 2.3.555-662
Hamlet and his mother, Gertrude, are discussing her relationship with Claudius. As this conversation is going on, Hamlet notices someone behind a curtain. He stabs through it, only to find out it is Polonius. It seems as if he has no remorse for his actions.
“Forty thousands brothers could not, with all their quantity of love, make up my sum” Shakespeare 5.1. 254-256
Hamlet jumps into Ophelia's grave and proclaims his love for her. Laertes confronts Hamlet, and challenges him to a duel. Laertes is distraught that his father is now dead and he knows Hamlet killed his father. He wants revenge.
"Here, thou incestuous, murderous, damned Dane, drink off this potion. Is thy union here?" Shakespeare 5.2.311
Hamlet kills King Claudius by stabbing him with the poisonous sword, and then forcing him to drink the poison that killed his mother. Hamlet and Laertes also die due to the poisonous sword.