Professor Terry Scott went to River Heights to ask the help of Carson Drew to help him to find Dr. Joshua Pitt. Mr. Drew thought that the case was more of a mystery, so he referred him to Nancy Drew, his daughter who loves detective work. Terry Scott and Dr. Joshua Pitt, together with their teammates, Dr. Anderson and Dr. Graham, found the clue to the treasure during their expedition in Mexico, a cipher carved in a stone tablet and three black keys. Before the professors had time to translate the cipher, the tablet disappeared together with Dr. Pitt, leaving only the bottom half of one of the keys. Terry suspected the Tinos because they vanished when the cipher stone and Dr. Pitt disappeared.