Teenage detectives Frank and Joe Hardy investigate a supposedly haunted house reported to be the hangout of criminals.

When they are invited to spend Christmas vacation at the private island retreat of wealthy Elroy Jefferson, the Hardy boys become involved in two mysteries: the disappearance of Mr. Jefferson's grandson and the theft of a priceless collection of antique medals.

Valuable electronic parts containing platinum are being stolen from shipments made by Stanwide Mining Equipment Company's cargo planes, and Frank and Joe Hardy are called upon to assist their world-renowned detective father to solve the baffling case. At Stanwide the boys pose as employees, and become suspicious of their boss's hostility toward them. Is he involved in the racket? And what is the truth behind the plane crash at sea in which Clint Hill,...

"Frank and Joe Hardy receive an unusual assignment from their detective father. They are to "break into" the house of a Bayport neighbor, Malcolm Wright, and retrieve a top-secret invention that the scientist had hidden in his study before leaving for California. The invention is in danger of being stolen, and the boys race against time to beat the thieves at their own game."--Flyleaf

The Hardy brothers solve the mystery of the missing inventor and recover some valuable missing jade.

A cryptic note from their father leads the Hardy boys to the Caribbean where they must solve the mystery, but only if they can successfully evade the henchmen who are trailing them.

In their motorboat the sleuths Frank and Joe Hardy search Barmet Bay for a dangerous stranger who has stolen a valuable boat. Suddenly, in the eerie fog, they spot the craft drifting aimlessly out to sea. What happens next starts the young detectives and their pal Chet Morton on an intriguing adventure that takes them to Mexico and into the comparatively unexplored desert and mountain regions of Baja California. The search for the meaning behind a...

While searching in Iceland for a missing sailor sought by an insurance company, the teen-age detective brothers uncover a plot threatening the life of a United States astronaut and the secrets of NASA's moon project.

The Hardy brothers interrupt their investigations of jewelry-store holdups to answer a plea from their cousin on a New Mexico cattle ranch. With only the slender clue of an arrow-shaped tie clasp, Frank and Joe Hardy pick up the trail of the cunning gang of thieves responsible for a wave of jewelry-store holdups. But their investigations are interrupted when a desperate plea for help comes from their widowed cousin who lives on a cattle ranch in...

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.