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

While investigating the theft of a valuable idol, Frank and Joe enounter a terrified business woman, a walking mummy, and a weird glass eye.

With only the slender clue of an arrow-shaped tie clasp, Frank and Joe Hardy pick up the trail of the cunning gang of thieves responsible for a wave of jewelry-store holdups. But their investigations are interrupted when a desperate plea for help comes from their widowed cousin who lives on a cattle ranch in New Mexico. Frank, Joe, and their pal Chet Morton fly there immediately. The mysterious disappearance of one cowboy after another has given Crowhead...

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

The Canadian Northwest beckons Frank and Joe Hardy to mystery and adventure. It all starts when a French-Canadian trapper, Caribou Caron, makes a historical and valuable find -- a carved rune stone left by Vikings centuries ago near Great Slave Lake. When Caribou Caron attempts to sell the artifact to a representative of a museum, it is snatched by thieves. Like the intrepid Vikings of old, Frank and Joe, with their close pal, Chet Morton, set off...

The Hardy brothers try to find out who is behind a rash of automobile thefts that are occurring on Shore Road just outside of Bayport.

Frank and Joe Hardy encounter the Footprints, an espionage ring which is attempting to steal a top-secret instrument paramount to a successful U.S. space program.

Frank and Joe uncover a plot to steal a vital top-secret instrument of the space program. They go off to jungle-filled islands to uncover a spy ring and recover their father's stolen documents.

Frank and Joe have many dangerous encounters in trying to find a missing professor and solving the case of suspected sabotage at a radar station.