She writes a random note:
“I have your son. If you want to see him again, tonight leave a bag with $500 under a park bench by the pond.
PS. No cops!
Realizing that she has no idea where to send it and not wanting to expose herself in the first place, she smartly sends the kid home to deliver her menacing missive.
The following morning she arrives at the designated bench and underneath finds a bag with the money and a note:
“How could you do this to your fellow Blonde???”