The bank president has disappeared -- and so has a big sum of money Are the disappearance of the president and the disappearance of the money related? And what does the strange symbol of the plumed serpent, found on some paper, have to do with it all? Penny searches for the answers to this and more in the Whispering Walls This book is from the Penny Parker series by Mildred A. Wirt, also known as ghostwriter Carolyn Keene, of the Nancy Drew series of books.