Franklin W Dixon

The Hardy boys' search for stolen gold leads them to an abandoned mine where, in the depths of the earth, they are attacked by outlaws.

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

While searching for the guard end of a broken saber that will solve one mystery, the Hardy brothers become involved with a gang of bank robbers.

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.

Hired to locate an old Spanish cannon, the Hardy brothers uncover an even greater treasure after perilous underwater adventures.

When the Hardy boys eagerly agree to assist their friend Jack Dodd and his father in locating a family treasure, the two young detectives are unaware of the baffling complications that will arise. The only clue to the long-lost treasure is a cryptic message written by a Pilgrim ancestor. But when Mr. Dodd and Jack are accused of stealing cars and then mysteriously disappear, Frank and Joe are confronted with a triple mystery. Have their friends run...

The search for a missing boat leads the Hardy boys and their father down to Mexico where they encounter a tribe of Indians.

Relates seven cases in which the Hardy brothers use police technology to track down criminals. Details of these techniques and procedures are given in the last five chapters.

Suspecting that their friend has been swindled, the Hardy brothers investigate and find themselves on the trail of a much larger criminal operation.

Frank and Joe travel to Philadelphia where they intend to prevent an attack on an extreme sports contest called the Big Air Games.