The Queen and Polonius are in her room. Polonius hides behind a curtain where he plans to eavesdrop on her conversation with Hamlet. Hamlet enters and begins to argue with his mother. She becomes frightened that Hamlet intends to harm her. She cries out and startled, Polonius echoes her cry. Thinking he is Claudius, Hamlet stabs Polonius through the curtain. He calls Polonius an intruding fool as he pulls his body into the open. The Queen is horrified and Hamlet tells her that his crime is almost as bad as hers. He is remorseful for his action but continues to berate his mother for her betrayal of his father. As she is begging him to stop, the Ghost appears but is visible only to Hamlet. The Queen thinks Hamlet's conversation with what appears to be thin air is produced by his madness. The Ghost reminds Hamlet of his purpose. Hamlet then entreats his mother to repent and abandon Claudius. He tells her of his suspicion that the trip to England is a plot against him and leaves, dragging the body of Polonius.
Hamlet: Novel Summary: Act 3, Scene 4