The Clue Of The Black Keys (Nancy Drew, Bk.28)

A young archaeology professor seeks Nancy's help in unearthing a secret of antiquity which can only be unlocked by three black keys. The young detective is plunged into an adventure that demands all her ingenuity and bravery as she and her friends follow a tangled trail of clues that lead to the Florida Keys and finally to Mexico. Again, Carolyn Keene has woven a suspense-filled story that will thrill her millions of readers.