Act III scene i: Claudius & Polonius spying on Ophelia & Hamlet
"No, not I. I never gave you aught"
The ghost was right!
Act III scene ii: The play that frightens King Claudius
"Give me some light!"
Act III scene iv: Hamlet kills Polonius
"O, what a rash and bloody deed this is!"
"How now, a rat?"
Claudius and Polonius eavesdrop to discover if the reason for Hamlet's madness is his love for Ophelia. Hamlet acts insane and tells Ophelia he never loved her.
A play troupe comes to Elsinore and performs The Mouse Trap, which is reenactment of King Hamlet's murder. When King Claudius sees the murder he is shocked and demands to be given some fresh air and light.
After Hamlet sees that King Claudius's murder of his father has been proven, he is furious that his mother married the murderer. While arguing he realizes someone is eavesdropping behind the curtain. So he stabs it hoping to kill Claudius, but instead kills Polonius.