After four fur trappers have been slain and their furs stolen, Corporal Rod Webb of the Royal Northwest Mounted Police sets out for their village. En route he and his dog Chinook come upon another trapper, Henri, shot and lying unconscious on the trail, and the furs he was delivering to the factor, McTavish, stolen. Chinook trails the would-be-killer Muskoka and bites a piece of cloth from his coat before he escapes. Webb leaves Henri with Greta while he investigates, aided by Minnetaki, Indian servant fired by McTavish, the real head of the fur thieves, and Marcia Cameron, wife of the superintendent of the trading company that employs McTavish.