Franklin Hardy (Frank Hardy) is an undercover agent of American Teens Against Crime (ATAC) and the older brother of Joe Hardy by one year, and the son of Fenton and Laura Hardy. The brothers live in the town of Bayport, with their parents and their father's unmarried sister, Trudy. Frank and Joe are top field agents for American Teens Against Crime, a top-secret government organization co-founded by Mr.Hardy. ATAC is used for cases where an adult law enforcement officer would be out of place.