Tony Prito enlists the help of his detective friends Frank and Joe Hardy when a sinister stranger demands that Tony sell him the bizarre curio collection he has just inherited.
While the boys are discussing the suspicious incident, the stranger, Valez, telephones and threatens Tony. That same afternoon the three boys collect the cases of curios at a freight station. On their way back to Tony's house an attempt is made on Joe's life. The next day a redhaired seaman claim the two medallions in the collection are his. But the medallions are missing! Did Valez steal them? And what are their significance?
Unraveling the clues in this exciting mystery takes the Hardys and their friends to a desolate region in Guatemala and straight into the hands of a gang of dangerous thugs.