A "monster" who terrorizes Bayport and a girl who runs away to join a cult are the subjects of the Hardy boys' sleuthing.

Frank and Joe try to stop someone from destroying Niagara Falls.

While participating in a Revolutionary War reenactment, Frank and Joe learn that there has been a real casualty and set out to investigate the incident.

Triggered by the disappearance of a brilliant young professor, this mystery takes the Hardy boys first to Kenworthy College, where they find a puzzling message on an examination paper. But then their pal Chet Morton, with his new metal detector, and buddy Biff Hooper, turn up a clue that sends the young detectives on an exciting search in another direction -- to the Honeycomb Caves, on the seacoast. A hot-tempered hermit who considers the caves his...

The Hardy boys' search for stolen gold leads them to an abandoned mine where, in the depths of the earth, they are attacked by outlaws.

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.

Frank and Joe are excited to learn that Thrill Kingdom, their local amusement park, is having a contest for kids to design a brand-new ride. And they're even more excited that their friend Phil is entering. But on the day of the contest, someone ruins Phil's roller coaster contest entry. Since it had been kept in a locked room while awaiting final judging it's up to Frank and Joe to figure out the twists and turns of this coaster caper!

The story begins with Frank and Joe Hardy barely avoiding being hit by a speeding driver whom they notice has bright red hair. Later, this same red-haired driver attempts a ferryboat ticket office robbery and successfully steals a yellow jalopy called Queen from the Hardys' friend, Chet Morton. Due to one witness reporting that the villain had dark hair, the Hardys assume he is using a red wig. It is learned that the thief returned to Chet's home...

Racing cars! Mystery! Adventure! These elements combine to give Frank and Joe Hardy one of the most dangerous and intriguing cases of their careers. It all starts when their father, Fenton Hardy, is engaged by an experimental race car and motor designer to investigate a series of mysterious accidents. Three of his drivers have crashed because the windshields of their cars were suddenly crazed, thus cutting off forward vision. Frank and Joe uncover...