While searching for the guard end of a broken saber that will solve one mystery, the Hardy brothers become involved with a gang of bank robbers.
After the new hydrofoil they are guarding is stolen, the Hardy boys face frequent danger in solving a mystery involving criminals who operate by signs of the zodiac.
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.
Once again Frank and Joe Hardy accept the challenge of a puzzling case when their famous detective father asks the boys to assist him in tracking down a notorious jewel thief and his accomplices.
Two unexplainable plane crashes near an airport on the East Coast lunge Frank and Joe Hardy into a bizarre. When their famous detective father is called to New York City by a group of insurance companies to investigate air freight thefts at Kennedy International Airport, Mr.Hardy asks Frank and Joe to take over his current case of the susppicious plane accidents.
A series of museum thefts lunch the Hardy Boys on this baffling mystery. Rare collection of ancient pirate treasure are being stolen. Who is doing it?And how is the loot being smuggled out of the United States?