Joe and Frank suspect there is a link between the counterfeiting case they are investigating, and the case their father can't discuss. Determined to learn the secret, the Hardy Boys get themselves into a scrape.

Timber wolves, a rocky Mountain blizzard, and a mine cave-in are only a few of the perils Frank and Joe Hardy encounter during their search for the notorious gang responsible for a payroll robbery.

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.

The dissapearance of a brillant young professor, a puzzling message on an examination paper, and a new metal detector have the Hardy boys searching for clues in the Honeycomb caves at the seacoast where they unexpectedly come upon a queer old hermit.

When their detective father asks them to play burglar in order to protect a client's valuable invention from thieves, the Hardy boys find themselves involved in a large and dangerous conspiracy.

The search for a stolen boat leads the Hardy brothers to Mexico where they become involved with a band of Indians and a strange smuggling operation.

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

The Hardy boys embark on another puzzling mystery when they try to discover who is stealing rare collections of ancient pirate treasure and smuggling them out of the United States.

After the new hydrofoil they are guarding is stolen, the Hardy boys face frequent danger in solving a mystery involving criminals who operate by signs of the zodiac.

When two suspicious plane accidents occur near an eastern airport, the two Hardy brothers investigate the case and find themselves in greater danger than they anticipated.