BEHIND THE GREEN DOOR is #4 in the Penny Parker Series by Mildred Wirt Benson.Penny visits a ski resort and stumbles upon several mysteries. Unknown enemies are trying to force the resort to close, and during her investigations, Penny discovers a mysterious green door in the resort that leads to a room that can only be entered by invitation.Mildred A. Wirt Benson (1905-2002) was a prolific author of books for young readers. A trained journalist, Benson is best known as a ghostwriter for the Stratemeyer Syndicate. Under the house pen-name Carolyn Keene, Benson completed 23 of the first 25 Nancy Drew mysteries and wrote a number of others until 1984. Benson also wrote her own mystery series, Penny Parker, from the 1930s to the 1950s.This unexpurgated edition contains the complete text, with minor errors and omissions corrected.