The art collector who suspects the Hardy boys of stealing one of his valuable paintings offers them a chance to find the painting and the real culprits.

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.

A "monster" who terrorizes Bayport and a girl who runs away to join a cult are the subjects of the Hardy boys' sleuthing.

Triggered by the disappearance of a brilliant young professor, this mystery takes the Hardy boys first to Kenworthy College, where they find a puzzling message on an examination paper. But then their pal Chet Morton, with his new metal detector, and buddy Biff Hooper, turn up a clue that sends the young detectives on an exciting search in another direction -- to the Honeycomb Caves, on the seacoast. A hot-tempered hermit who considers the caves his...

The Hardy boys' search for stolen gold leads them to an abandoned mine where, in the depths of the earth, they are attacked by outlaws.

While investigating the theft of a valuable idol, Frank and Joe enounter a terrified business woman, a walking mummy, and a weird glass eye.

A trained peregrine falcon that the young detectives receive as a gift involves them in an exciting mystery. Imagine their astonishment when the swift-flying falcon brings down a homing pigeon carrying two precious rubies! Startling events that ensue indicate the gems are part of a ransom that has been paid for the release of the kidnapped student from India, who had come to the United States to complete his education. But Tava Nayyar, the son of...

Their search for an Easter Island idol takes the Hardy boys to Easter Island and on to investigate the theft of government material in Antarctica.

The search for a stolen boat leads the Hardy brothers to Mexico where they become involved with a band of Indians and a strange smuggling operation.

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.