Digging up history

"When a summer intern at the Preservation Society discovers an aged document hidden in the binding of an antique book, Society president Nell Pratt is intrigued by the possibilities: is it a valuable historic document or just a useless scrap of paper? When analysis reveals that it's a hand-drawn map of one of Philadelphia's oldest neighborhoods, Nell learns that the area is being excavated for a new real estate development and may hold long-burie...