New York City. Central Park. For thousands of residents and tourists who fill it every day, it’s an enormous urban sanctuary. For one killer it’s the perfect hunting ground.   A young girl has been found dead in the Ramble, a secluded section of the park made up of winding paths, dense woods, and dead ends. Is she the first victim of a psychopath? Or a clue to other missing women in years past whose remains have never been found?   For the answer, Assistant DA Alexandra Coope