When Mr. Hardy disappears while investigating a mystery surrounding a vacant house rumored to be either haunted or an abode for criminals, Joe and Frank search for the truth.

During their search for members of a notorious gang responsible for a payroll robbery, Joe and Frank Hardy encounter timber wolves, a Rocky Mountain blizzard and a mine cave-in.

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

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

The Hardy brothers' search for the missing son of a wealthy industrialist leads them to Brazil and great danger.

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.

Frank and Joe attempt to foil a ruthless espionage ring in their effort to sabotage the United States space program.

The Hardy boys and two friends take a camping trip to the Rocky Mountains in an attempt to locate a gang of credit-card counterfeiters.

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,...