Hamlet mistakes Polonius' voice for Claudius' and stabs him through the curtain and kills him.
How now, a rat? Dead for a ducat, dead! (3. 4. 29)
Gertrude encounters Claudius and tells him that Hamlet killed Polonius. Claudius decides to send Hamlet to England.
Mad as the sea and wind when both contend/which is the mightier. In his lawless fit,/behind the arras hearing something stir,/whips out his rapier, cries ‘A rat, a rat’,/and in this brainish apprehension kills the unseen good old man.” (4. 1. 7-12)
Hamlet gets rid of Polonius' body, and Rosencrantz and Guildenstern question him about Polonius.
The body is with the king, but the king is not with the/body. The kind is a thing-.” (4. 2. 24-25)
Rosencrantz and Guildenstern bring Hamlet to Claudius to get him to tell where Polonius' body is. Hamlet begins to tell them that Polonius was eaten by worms.
Claudius sends Rosencrantz and Guildenstern to take Hamlet to the ship to go to England.
Fortinbras leads his army through Denmark, and plans to attack Poland. He runs into Rosencrantz, Guildenstern, and Hamlet on the way to ask the King to grant him permission to pass through Denmark.