Two unexplainable plane crashes near an airport on the East Coast plunge Frank and Joe Hardy into a bizarre case. From the moment Frank and Joe find a radioactive engine in an airplane junkyard, unexpected dangers strike like lightning. Despite the repeated attempts on their lives, the teenage detectives pursue their investigation, discovering two vital clues and others that provide the solution to one of the most baffling mysteries the boys and Mr. Hardy have ever encountered.

When two suspicious plane accidents occur near an eastern airport, the two Hardy brothers investigate the case and find themselves in greater danger than they anticipated.

When an ancient stone idol disappears, the Hardy Boys are off on another fast-paced adventure. It's a mystery that takes the boys from a primitive village in the Andes Mountains to Antarctica and finally to Easter Island. By using their fine investigative skills, the Hardy Boys find that the mystery of the stone idol is not what it seems!

When a man selling leather goods door-to-door steals the key to their detective father’s file cabinet, Frank and Joe Hardy set out to track him down. An odd mark on a key case which the man sold to their mother leads the teenage sleuths to an Indian village, whose chiefs begs them to help him find valuable tribal possessions and the deed for his land. How Frank and Joe find the missing deed and Ramapan treasures, how they prevent the phony leather-goods salesman from carrying out a ruthless scheme and how they help their father solve the top-secret case he is working on for the U.S. government makes exciting reading for all fans of the Hardy boys.