When the Hardy Boys set out to solve the mystery of their missing chums, they discover a gang hide-out in a cave on an island along the way.

When Mr. Hardy disappears while investigating a mystery surrounding a vacant house rumored to be either haunted or an abode for criminals, Joe and Frank search for the truth.

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

Joe, Frank, and their friends search the icebound Cabin Island for a missing boy and some stolen medals.

When Frank and Joe try to get hold of a top secret invention, they are put on the trail of jewel thieves and smugglers. Joe is kidnapped and Frank starts off on the chase.

During their search for members of a notorious gang responsible for a payroll robbery, Joe and Frank Hardy encounter timber wolves, a Rocky Mountain blizzard and a mine cave-in.

When someone is out to frame Frank and Joe for the theft of an original Sherlock Holmes manuscript, they use a group of skateboarders as sources of information in their attempt to clear their names.

Brother detectives Frank and Joe face the dangers of Black Bear Mountain once again in the twentieth book in the thrilling Hardy Boys Adventures series.
Frank and Joe are back on Black Bear Mountain, the scene of a previous wilderness adventure and mind-bending mystery. This time, the brothers are checking in on Dr. K, a friend they made during their first trip. Dr. K is a fan of living off the grid, but he's been MIA long enough to cause...