Three young forest rangers patrol remote timberlands and repeatedly face criminals, arson, and puzzles. An early reward funds their outfitting and they gain an old guide’s friendship while earning the enmity of a vindictive halfbreed who continually menaces them. They rescue a kidnapped child, follow ciphered notes from an enigmatic hermit, foil fur smugglers on the border, and discover a rich tourmaline deposit by solving a torn map. Later they expose timber thefts at a logging camp, employ a wireless telephone to aid rescues, and pursue clues to one youth’s family mystery.