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

When a crime syndicate takes over Bayport's reservoir Frank and Joe Hardy help their detective father solve the sinister mystery.

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

On an ice-bound, snow-covered island, Frank and Joe attempt to solve the mystery of a boy's disappearance and the theft of a priceless collection of antique medals.

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...

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.

While on a relaxing safari vacation to Nairobi, Frank and Joe Hardy become involved in finding the culprits responsible for killing innocent animals for their tusks and skins.

After the assistant principal discovers the answers to a new statewide test in Tony's bookbag and Joe protests that Tony did not try to cheat, they are both suspended, leading the Hardy boys to search for the real culprit.

Frank and Joe Hardy must retrieve a top-secret invention that a scientist had hidden in his study. Their investigations put them on the trail of jewel thieves and smugglers.