Franklin W. Dixon

"Drop case or else danger for you and your family." This warning addressed to Fenton Hardy not only alarms the famous investigator and his detective sons, but also puzzles them, because Mr. Hardy is working on more than one case. Which one prompted the threat? When more ominous warnings follow, Frank and Joe suspect there is a link between the counterfeiting case they are investigating and a secret case their father cannot discuss since it involves...

Hired to locate an old Spanish cannon, the Hardy brothers uncover an even greater treasure after perilous underwater adventures.

In solving the mystery of two medallions missing from an inherited curio collection, the Hardys wind up in a desolate area of Guatemala at the mercy of dangerous thugs.

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...

Fenton Hardy, the famous private detective and father of the Hardy Boys, asks his sons to help him with his latest case involving a criminal named Snattman and the illegal drug trade smuggling of stolen drugs. Hardy directs Frank and Joe to a house on the cliff, whose location overlooking Barmet Bay offers an excellent vantage point to watch for smugglers. The Hardys are tricked into the house by cries for help, and are trapped for a short time in...

The Hardy boys and their father solve a mystery involving inexplicable crashes of highspeed race cars being used to test an experimental turbine motor.

While Frank and Joe help their father locate a notorious jewel thief, they also explore the mysterious death of a tycoon's nephew years before.

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.

Valuable antique weathervanes are being stolen in the Pennsylvania Dutch country. A Navy employee removes a top secret document from the Pentagon. The Hardy brothers try to solve these two seemingly unrelated mysteries.

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 principal members of a notorious gang responsible for a payroll robbery. In the old Montana mining camp of Lucky Lode, the young detectives puzzle over a series of mysterious events. A piano-playing ghost haunts the long-abandoned dance hall. Eerie blue lights flash from the hilltop cemetery in the dark...