Identity theft

What is the mysterious organization known as ATAC (American Teenagers Against Crime)? And how are detective brothers Frank, Joe, and Fenton Hardy involved? Uncover the clues to these questions as the Hardy brothers take to the skies to crack a diamond-smuggling team of sky-divers and then encounter a young woman whose identity has been stolen (or at least that's what a young woman claiming to be Joy Gallagher claims).