The Canadian Northwest beckons Frank and Joe Hardy to mystery and adventure. It all starts when a French-Canadian trapper, Caribou Caron, makes a historical and valuable find–-a carved rune stone left by Vikings centuries ago near Great Slave Lake. When Caribou Caron attempts to sell the artifact to a representative of a museum, it is snatched by thieves. Like the intrepid Vikings of old, Frank and Joe, with their close pal Chet Morton, set off on a perilous quest in the Northwest Territories to recover the valuable artifact before the robbers can decipher the symbols leading to the buried treasure.

Frank and Joe Hardy meet many adventures while trying to recover a valuable stolen artifact in the Northwest Territories

Danger is the name of the game when the Hardys agree to help their pen pal from Greece, Evan Pandropolos, search for a priceless, ancient Greek helmet. Years ago, Evan’s uncle had loaned it to Hollywood movie company for use in a silent motion picture, but the treasured helmet had been lost. Picking up foes along the way, the young detectives unearth clues that keep them constantly on the move—from their Greek college campus to California and finally to Greece.

During Mr. Hardy’s investigation of a ruthless gang of terrorists, Frank and Joe witness an explosion in the sky near an airborne dirigible owned by Quinn Air Fleet. The young detectives look into a clue that takes them into a new animal park outside Bayport, where they are lured into a trap by an unknown enemy. Problems arise for the park owner as he receives pressure from a competitor and a real-estate firm to sell out. Strange occurrences at the park also frighten the visitors and animals. Frank and Joe take up the case despite fore warnings.

In a search for the missing Willard Grafton, Frank Hardy and younger brother Joe, encounter a gang of criminals intent on defrauding the US government, and are lead across California and even into Mexico.

When an ancient stone idol disappears, the Hardy Boys are off on another fast-paced adventure. It's a mystery that takes the boys from a primitive village in the Andes Mountains to Antarctica and finally to Easter Island. By using their fine investigative skills, the Hardy Boys find that the mystery of the stone idol is not what it seems!

When she is told that a large inheritance from a Greek tycoon, meant for her friend Helen Nicholas, was stolen, Nancy agrees to find the culprit. A poisonous snake in a basket of apples and a strange symbol stamped on a rare Byzantine mask are clues in this mystery set in the beautiful and exotic country of Greece. These clues lead Nancy and her friends to a ring of art smugglers and to the secret of the Greek symbol.