THE CLUE OF THE BACK KEYS (NANCY DREW) HARDCOVER
During an archaeological expedition in Mexico, two professors, the senior Dr. Joshua Pitt and young Terry Scott find a clue to buried treasure. The clue was a cipher carved on a stone tablet. Before the older professor had time to translate it, he and the tablet disappeared! Terry tells Nancy of his suspicions of a Mexican couple, posing as scientists, who vanished the same night as Dr. Pitt. Nancy follows a tangled trail of clues that lead to Florida and Mexico and a secret of antiquity that can only be unlocked by three black keys. 1968 EDITION Grosset & Dunlap