Vicious threats and deadly traps beset Frank, Joe and Chet as they search for clues to the stolen paintings and the gold treasure--a search that is complicated by a stormy feud between a proud Englishman and an equally proud Franchman over the military history of the ancient fort.

When the Hardy boys set out to investigate the disappearance of Mr. Grafton, they become involved in capturing a gang of counterfeiters.

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.

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

When Frank and Joe try to get hold of a top secret invention, they are put on the trail of jewel thieves and smugglers. Joe is kidnapped and Frank starts off on the chase.

After a dying criminal confesses that his loot has been stashed "in the tower", the Hardy boys make an astonishing discovery.,

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.

Their efforts to recover a stolen ancient chess piece lead the Hardy brothers to Hong Kong where they help smash an international criminal organization.

The Hardy boys' investigation of a museum robbery in England arouses the anger of a coven of black witches. There is no time for explanations when Mr. Hardy telephones Frank and Joe from the West Coast and sends them flying off to England to help his old friend Professor Rowbotham. Their stay in East Anglia begins with a weird omen, as they witness the bizarre funeral of an old witchmaster. From then on, strange things happen. They are shadowed,...

When the Hardy Boys set out to solve the mystery of their missing chums, they discover a gang hide-out in a cave on an island along the way.