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.,

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.

After many dangerous encounters, including a nearly disastrous patrol on the stormy ocean, Frank and Joe discover a powerful searchlight in one of the craggy caverns along the seacoast. In the brilliant white glare of the searchlight, the startling secret of the caves is dramatically revealed.

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

Vicious threats and deadly traps beset Frank, Joe and Chet as they search for clues to the stolen paintings and the gold treasure--a search that is complicated by a stormy feud between a proud Englishman and an equally proud Franchman over the military history of the ancient fort.

The Hardy boys dial a wrong number, get the Pentagon, and suddenly find themselves in a dangerous adventure involving national security.

In the Northwest Territories of Canada, the Hardy brothers and Chet Morton help to recover a stolen Viking relic.

Frank and Joe investigate a walled estate guarded by savage dogs, where a businessman is hiding in fear of his life.

When their peregrine falcon brings down a homing pigeon carrying rubies, the Hardy brothers find themselves involved with kidnappers.