Cordelia is a human girl raised by squirrels in Central Park and well-known among the park's other critters. When she gets an urgent message summoning her to the Central Park Zoo, Cordelia learns from the sea lions that a monster has been roaming the park grounds--something the size of a bear with glowing eyes!

With the help of her best friend, Isaac, Cordelia sets out to trap this mystery creature. They follow a string of questionable leads taking them to a dog park, a parade, and even an encounter with the New York Yankees! But can they find the Central Park Ghost?