Aunt Eloise Drew invited Nancy and her friends to Mirror Bay Bide-a-Wee
cabin near Cooperstown, New York, for a visit and a chance to solve the
mystery of the woman who glides across the water. Upon their arrival,
Nancy becomes mixed up in a vacation hoax and is nearly arrested for
fraud.
On the wooded mountain near the cabin further exciting events await
Nancy and the other girls. In the deep forest, a weird luminescent green
sorcerer appears who threatens to cast an evil spell on anyone
investigating his strange activities. In a dangerous twist of
circumstances Nancy finds that solving one mystery helps to solve
another. What happens when the young detective and her friends uncover a
cleverly concealed criminal operation?