At the end of the play, Hamlet agrees to a fencing match with Laertes. He doesn't realize that Claudius and Laertes are working together to plot against him and have no intention of letting Hamlet live through the fencing match. They have laced the tip of Laertes's sword with...
At the end of the play, Hamlet agrees to a fencing match with Laertes. He doesn't realize that Claudius and Laertes are working together to plot against him and have no intention of letting Hamlet live through the fencing match. They have laced the tip of Laertes's sword with poison to ensure that even the smallest scratch will be fatal. As a backup plan—in case Laertes fails to wound Hamlet—Claudius has laced Hamlet's drink with more poison.
As Hamlet and Laertes begin to fence, Claudius offers Hamlet the poison-laced cup, but Hamlet refuses it. Unfortunately, Gertrude (Hamlet's mother and Claudius's wife) drinks from the cup instead, unaware it is poisoned. After a few hits, Laertes and Hamlet end up in a scuffle, and Hamlet inadvertently ends up with Laertes's poison-tipped sword, injuring Laertes with it after being injured himself. Gertrude falls to the floor as the poison takes effect.
Hamlet isn't aware of the gravity of the situation until Laertes, aware that they are both about to die, confesses what he and Claudius have done:
It is here, Hamlet. Hamlet, thou art slain.
No medicine in the world can do thee good.
In thee there is not half an hour of life.
The treacherous instrument is in thy hand,
Unbated and envenomed. The foul practice
Hath turned itself on me. Lo, here I lie,
Never to rise again. Thy mother’s poisoned.
I can no more. The king, the king’s to blame (V.ii.342).
Laertes dies first, and Hamlet has a few final (and dramatic, of course) moments to process his imminent death. Finally spurred into action, Hamlet forces Claudius to drink his own poison and runs him through with the sword.
As he succumbs to the poison, Hamlet forgives Laertes and acknowledges that Fortinbras is likely the next leader of Denmark. He asks that Horatio tell Fortinbras what has happened at the castle, and then he dies.