A series of robberies have taken place at Highview Hospital, robberies which involved expert knowledge of . Three High School boys formed themselves into a club called the Tri- and elected to help the detective on the case. One clue same to their knowledge -- the chief robber could be identified by a gold tooth. And to their ment, they noticed -- at a picnic -- that the head of the hospital staff had a gold tooth identically placed. Their suspicions had further confirmation when Foxy was virtually forced to drive the doctor and a friend to their hideout. The other boys went for help and used a homemade whistle to attract Foxy's dog. And the mystery was solved.