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

Teenage detectives Frank and Joe Hardy investigate a case of counterfeiting

Their SOS ignored in a storm, the Hardy boys find a wallet containing two thousand dollars alongside their boat and are launched into a mystery involving diverse clues

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.

SOMETIMES THE BEST ACTING IS DONE BY AMATEURS The Hardys' friend Chet answers an ad in the paper for a role in a student film. There's just one catch: All participants must have a boat, so Chet persuades Frank and Joe to get their motorboat, the Sleuth, out of mothballs. He even convinces the brothers to join him. The aquatic extravaganza will be shot locally on Barmet Bay and will be totally improvised. The director promises clues, cryptic charts,...

When the Hardy boys reached the caves, they came unexpectedly upon a queer old hermit.

"A cooking competition goes wrong when a storm traps both the Hardy brothers and a criminal on the small Rubble Island"--

Frank and Joe Hardy search a mysterious castle for clues to a stolen, extremely valuable comic book.

"Frank and Joe are off to the Florida Keys to work alongside Lookout Shark Lab's Dr. E. Ella Edwards, one of the world's foremost marine biologists. On their first evening, Dr. Edwards paddleboards out to check on a lemon shark nursery. But after a sudden squall rolls in, she doesn't return, and the next day her board washes up with a shark bite taken out of it. The Hardys volunteer to help the search and rescue efforts as panic sparks a rift in Lookout...

Frank and Joe investigate a series of robberies in Philadelphia