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 fin – 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 Viking 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.