When their detective father asks them to play burglar in order to protect a client's valuable invention from thieves, the Hardy boys find themselves involved in a large and dangerous conspiracy.

Frank and Joe Hardy are determined to bring to justice the vicious criminals who kidnapped their detective father while he was investigating sabotage of a road-building project in the Kentucky wilderness. After Mr. Hardy's amazing escape, the boys pick up a clue -- the word "Felix" mumbled by their sick father in his delirium. When they discover that the dossier of a notorious ex-convict has been stolen from Mr. Hardy's files, the two young sleuths...

The Hardy boys embark on another puzzling mystery when they try to discover who is stealing rare collections of ancient pirate treasure and smuggling them out of the United States.

The Hardy boys travel to the Deep South to vindicate a long-dead Confederate general, disgraced during the Civil War because he was accused of stealing hidden gold belonging to a bank.

Caught in their motorboat the Sleuth by a sudden storm at sea, Frank and Joe Hardy are helpless when the engine conks out. Drifting farther from shore amid the tumultuous waves, the boys are relieved to see the lights of a yacht. But their SOS is ignored. The shrill sound of a siren fills the night air. Moments later, a helicopter drops an object alongside the Sleuth. To the young detectives' astonishment it proves to be a wallet containing two thousand...

Frank and Joe investigate the legend of Whalebone Island when they receive a warning concerning a sunken freighter.

During their father's investigation of a ruthless gang of terrorists, two young detectives face several adversaries.

In the Northwest Territories of Canada, the Hardy brothers and Chet Morton help to recover a stolen Viking relic.

When they journey to Alaska to help a friend who feels his life is in danger, the Hardy brothers find their own lives threatened.

When a new combat sports training facility opens in Bayport, Frank and Joe enjoy having somewhere to practice judo, fencing, archery, and biathlon, until a series of accidents leads them to investigate, suspecting sabotage.