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

When their detective father asks them to play burglar in order to protect a client's valuable invention from thieves, the Hardy boys find themselves involved in a large and dangerous conspiracy.

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

During their father's investigation of a ruthless gang of terrorists, two young detectives face several adversaries.

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.

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.

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 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.

An archaeological expedition in the West turns into a desperate attempt to capture robbers and an escaped convict.

There is a crisis in Bayport! Soon the city will be without water! Every night water strangely disappears from the new reservoir near Skull Mountain. Frank and Joe Hardy join forces with thteam of skilled engineers to solve the baffling mystery. When the boys arrive at the foot of the mountain, they are met by a human skull rolling down the slope -- a chilling warning from a weird hermit. Violence, too, stalks the mountain, where a gang controlled...