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The Hardy boys agree to help a friend and his father find a family treasure. When the friends disappear, the sleuths find themselves faced with two mysteries.

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A banker who has been receiving threatening notes enlists the help of the Hardy boys. Before very long, the young sleuths find themselves entangled in the investigation of a notorious band of thieves.

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In an effort to recover a top-secret instrument needed by the space program, the Hardy boys travel to South America, hot on the trail of a notorious ring of spies.

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The search for a missing boat leads the Hardy boys and their father down to Mexico where they encounter a tribe of Indians.

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

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A blind peddler's warning and a glass eye plunge Frank and Joe Hardy into a baffling case.

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The owner of a gold pharaoh's head claims it was aboard the freighter Katawa, but suspicions arise that he is trying to defraud the shipping line's insurance company.

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When their father asks for help tracking a jewel thief, the Hardy boys find that the trail leads them back to their own hometown. There, they begin a new investigation of a mysterious death which occurred many years ago.

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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.

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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.

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Suspecting that their friend has been swindled, the Hardy brothers investigate and find themselves on the trail of a much larger criminal operation.

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The theft of a collection of stuffed animals from a country auction draws Frank and Joe Hardy into a thrilling mystery.

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The Hardy brothers embark on a freighter trip under mysterious circrcumstances and find themselves involved with a smuggling ring.

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The Hardys team up with a team of engineers to discover how water is disappearing from Bayport's new reservoir near Skull Mountain.

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The Hardy brothers interrupt their investigations of jewelry-store holdups to answer a plea from their cousin on a New Mexico cattle ranch.

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The Hardy brothers accept the challenge of vindicating a Confederate general accused of stealing hidden gold which belonged to a a bank.

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Stranded by a sudden storm at sea, the Hardy boys discover a wallet containing two thousand dollars. Upon returning home, they learn that a truck loaded with rifles has been stolen. Even though the two events seem unrelated, they are but the first clues in a complex mystery.

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The Hardy boys follow a thief to a Native American village. There, the residents ask for the boys' help in recovering the deed to their land before the land is claimed by strangers.

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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.

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

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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.