Franklin W Dixon

Teenage detectives Frank and Joe Hardy investigate a case of counterfeiting.

Triggered by the disappearance of a brilliant young professor, this mystery takes the Hardy boys first to Kenworthy College, where they find a puzzling message on an examination paper. But then their pal Chet Morton, with his new metal detector, and buddy Biff Hooper, turn up a clue that sends the young detectives on an exciting search in another direction -- to the Honeycomb Caves, on the seacoast. A hot-tempered hermit who considers the caves his...

The Hardy brothers' visiting Greek pen pal enlists their help in searching for a priceless ancient Greek helmet loaned to and lost by a Hollywood movie company years before.

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

While searching in Iceland for a missing sailor sought by an insurance company, the teen-age detective brothers uncover a plot threatening the life of a United States astronaut and the secrets of NASA's moon project.

Frank and Joe, the Hardy boys, solve a mystery involving a magician, American secret agents, and international spy ring, and a Scottish castle.

Two teenage sleuths help their detective father search for a famous rocket scientist whose disappearance endangers the launching of the Firebird Rocket.

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