The Aldens learn that their housekeeper, Mrs. McGregor, has to sell her childhood home, the Crooked House, because she and her sister Madeline cannot afford to keep it. They travel to visit the house, now a bed-and-breakfast run by Madeline, one last time. While there, the Aldens learn that there is a riddle surrounding the house, and if they can solve it, there might be a treasure to be found! Illustrations.