Franklin W. Dixon 
Mark of the Blue Tattoo 

Chet Mortons very first day on the jobdriving a Freddy Frost Ice Cream trucksends him straight into the deep freeze. Two thugs in ski masks hijack the truck and kidnap Chet! Frank and Joe find him tied up in an empty garage, and the only clue to the identity of his kidnappers is the blue star tattooed on their wriststhe mark of the Starz. A local street gang.