Eloise Drew invites her niece and the cousins to a cabin near Cooperstown, New York to solve the mystery of a woman who glides across the water. Upon arriving, Nancy becomes involved in a vacation hoax when she is mistaken for a woman in on the fraud. On the wooded mountain near the cabin, a weird luminescent green sorcerer appears, threatening to cast an evil spell on those investigating his strange activities. A lost treasure involving the gliding woman leads Nancy to uncover a cleverly concealed criminal operation in the woods. This book is the original text. A revised text does not exist.