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 this suspicious incident, the stranger, Valez, telephones and threatens Tony. That same afternoon the three boys collect the cases of curios at a freight station only for Joe's life to be at risk on their way back to Tony's house. The next day a seaman claims two medallions in the collection that coincidently go missing. Did Valez steal them? And what was 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.