In the Canadian Northwest, Paul Latrec, a French-Canadian fur trapper, finds the murdered bodies of fellow trapper Gaston LaFontaine and his wife in their cabin, their furs missing and their infant baby abandoned. Paul takes the infant to town to be reared by with his sweetheart Renée and there reports the murders to J. L. McTavish, the factor of the trading post. McTavish, who lusts after Renée, is secretly in league with the LaFontaines' murderer, Muskoka, who has stashed the stolen furs in the ice house behind the trading post. Planning to frame Paul for the murders, McTavish offers him $500 to deliver the furs to a trading post on the other side of the mountains. As Paul traverses the treacherous mountain pass, Muskoka follows, dispatched by McTavish to kill Paul. Meanwhile, Mountie Rod Webb and his trusty white dog Chinook arrive to investigate the rash of thefts and murders that have been plaguing the area. When Muskoka shoots Paul, Chinook and Rod hear the gunfire and rush to determine its source. Chinook arrives first and lunges at Muskoka, ripping a patch from his jacket and sending him scurrying into the woods for cover. While Rod nurses the wounded Paul back to health in the woods, Edward Cameron, the superintendent of the trading post, arrives in town to examine McTavish's books and becomes alarmed at the losses incurred because of the robberies. Cameron's shrewish wife Marcia, meanwhile, criticizes the housekeeping of McTavish's Indian servant Minnetaki and demands her immediate dismissal. Learning of Minnetaki's plight, the sympathetic Renée invites her to live in her cabin and help care for the baby. After Muskoka reports back that he has successfully eliminated Paul, McTavish informs Cameron and Renée that Paul sold the furs and absconded with the proceeds. Soon after, Paul and Rod appear at Renée's cabin. When Renée tells Paul that McTavish accused him of stealing the furs, Rod, suspicious, instructs Paul to stay out of sight while he visits McTavish. After Rod leaves, Paul lets Chinook out of the house and Muskoka recognizes the dog as his assailant. When Muskoka goes to McTavish's office to report Chinook's presence, Marcia recognizes him as the furtive figure she saw in the woods and suspects that he and McTavish are involved in some sort of illegal activties. Muskoka follows Rod back to Renée's house and spies Paul from the window. After Rod departs, Muskoka hurls a knife into Paul's back, but only wounds him. The next day, McTavish sees Chinook romping around town and realizes that Paul must still be alive. Deciding to set a trap for the murderer, Rod shows McTavish the scrap of material that Chinook seized from the jacket of Paul's assailant. That night, Muskoka slips into the cabin and steals the patch. The next morning, Rod appears at the trading post with Paul and proclaims Paul's innocence. Afterward, Rod searches Muskoka's cabin and finds the ashes from the coat he tried to burn in the fireplace. Meanwhile, Renée and Minnetaki go to the trading place for supplies. When Minnetaki returns to the cabin alone, she is threatened by Muskoka, causing Chinook to attack him. As man and dog tangle, Minnetaki grabs the baby and flees. After Chinook chases Muskoka into the woods, Renée returns and, finding a puddle of blood on the floor and the baby missing, assumes that Chinook killed the baby. Renée charges Chinook with murder, and sends Paul after the dog. Gravely injured by Chinook's attack, Muskoka, meanwhile, collapses in the woods and is found by Rod. With his dying breath, Muskoka identifies McTavish as the man behind the robberies and murders. Soon after, Minnetaki returns the baby to Renée, who realizing her mistake, hurries to apologize to Chinook. After Rod comes to the trading post in search of McTavish, Marcia warns McTavish that the Mountie knows he is the killer. McTavish flees into the woods and is pursued by Chinook and Rod. After a rousing fight in the river bed, Rod routs McTavish and brings him to justice.