the hardy boys are drawn into a mystery when a group of thieves steals a collection of stuffed animals from an estate sale. later, the hardy boys notice a station wagon carrying stuffed animals, but when they try to give chase, the car gets away, leaving only a broken ham radio antenna behind. while they are discussing the case that their father fenton hardy is working on, they learn that he is after a group involved in industrial espionage and that this group uses code words very similar to what the boys have been hearing transmitted over the ham radio bands.