After the new hydrofoil they are guarding is stolen, the Hardy boys face frequent danger in solving a mystery involving criminals who operate by signs of the zodiac.

The Hardy boys find mystery in the Canadian Northwest when a carved rune stone left by Vikings is found near Great Slave Lake.

No sooner do Frank and Joe Hardy, America's favorite teen detectives, rescue a family from a flash flood, than they're off on a new top-secret ATAC (American Teens Against Crime) mission. Frank and Joe must go undercover on a new reality TV show called 'Madhouse,' to discover how far the producers are willing to go risking the contestants' lives for the sake of huge ratings. The plot thickens when the producer of Madhouse turns up murdered!

"Frank and Joe go undercover at a national spelling bee where a mysterious madman known as the Hangman is determined to erase the competition! Teens from across the globe have been invited to attend, and A.T.A.C. and the Hardy Boys have to do everything they can to keep the Hangman from spelling disaster!" -- fromn publisher's web site.

When Frank and Joe are assigned to safeguard the children of a visiting dignitary as they go on a visit to the National Library of Education, they look to their librarian mother for aid.

A.T.A.C.'s top agents, Frank and Joe Hardy, go undercover on the hit reality TV series, "Break-Up," to find out why a contestant has mysteriously died--but will this turn out to be the Hardy Boys' last case? If being on the show doesn't kill them, will the strain of working together tear the Undercover Brothers apart?

Frank and Joe Hardy investigate the disappearance of several teens at a "tough love" western camp.