In the woods of Canada, Sgt. Mike Malone of the Royal Canadian Mounties tracks down a young French Canadian woman, Rose Marie Lemaitre, and tells her he promised her late father he would take her to Fort Macroy. After attempting to flee, Rose Marie begs Mike to let her remain in the wilderness that has always been her home, but he maintains that the rough life of the woods is not suitable for a girl. Mike introduces Rose Marie to the other men that night at dinner, but when she rebelliously dumps a bowl of soup on his head and bites him, Mike locks her in the brig, under the supervision of the hapless Barney McCorkle, the oldest corporal in the Mounties. Gradually, however, Rose Marie settles into her new life with the Mounties and develops an affection for Mike. One day, Inspector Appleby comes to review Mike's troops, and is appalled to find Rose Marie in uniform. Appleby upbraids Mike for letting a woman live with the Mounties, and Mike admits he has only ever thought of Rose Marie as a child. Appleby proposes that Rose Marie be sent to live with his cousin in Maple Rock, but she refuses to give up her freedom to live like a lady, and runs away. Mike goes after her and explains that she is becoming a beautiful woman and will someday be interested in men. While riding back to the fort, Mike and Rose Marie encounter renegade trapper James Severn Duval, and Rose Marie is attracted to him at once. Mike takes Rose Marie to the Northern Lights Hotel in Maple Rock, and delivers her into the care of bawdy proprietress Lady Jane Dunstock. Jane treats Rose Marie like a daughter and gives her lessons in dressing and behaving like a young lady. One day, Rose Marie sees James in the street and invites him to a dance that evening. James then visits an Indian village, where he is greeted by Wanda, a pretty young woman who is in love with him. James calls on Chief Black Eagle, who frowns on the white man's friendship with Wanda, and gives him the money the chief requested the previous year for a piece of land on the river. When Black Eagle tells him the price of the land has now doubled, James angrily vows to return with the money. That night, James steals the money collected at the dance, but when Rose Marie tells him the money was for charity, he gives it back. Late that night, Rose Marie sneaks away to the woods and finds James, and they begin to fall in love. James returns to Black Eagle and proposes that the chief give him the land in exchange for half of the mineral rights, but Black Eagle refuses. Mike is waiting outside when James leaves the chief's tent, and warns him to stay away from Rose Marie. Mike later calls on Rose Marie and proposes. Rose Marie confesses she has never thought of him romantically, but Mike kisses her and urges her to consider his offer. That evening, James climbs up to Rose Marie's balcony and takes her to the Indian Totem Festival of Summer. While watching the native dancing, they share a passionate kiss under Wanda's jealous glare. James brings Rose Marie home and tells her he must go away to resume his trapping, and asks her to accompany him. James then retires to his shack near Jane's house, unaware that Wanda has followed him from the Indian village. Wanda creeps in and is about to stab James with his own knife when Rose Marie comes in to say she will meet James at his camp the following day. James tells Rose Marie that if she changes her mind about going away with him, she is to signal him by singing the Indian love song. When Wanda returns to the village that night, Black Eagle angrily begins to whip her, and she stabs him, then flees in horror. The Mounties are called in to investigate, and when Mike shows Rose Marie the knife used to kill the chief, she recognizes it as James's. To protect James, Rose Marie rides to the woods and tearfully sings the Indian love song to send him away. James is captured by the Indians, however, and Mike arrives just as they are starting to burn him at the stake. Mike rescues James and arrests him for murder, and the trapper is convicted and sentenced to hang. Rose Marie pleads with Mike to intervene, declaring her love for James and faith in his innocence. Although he is crushed by this revelation, Mike reexamines the case, and when he and Barney find an Indian love ring among James's effects, they suspect a jealous lover. Mike confronts Wanda and tricks her into confessing, and James is set free. For his help in solving the crime, Barney is at last promoted to sergeant. After James's release, the grateful Rose Marie tells Mike she will do anything he wishes. Mike tells Rose Marie to put on her buckskins and go for a ride with him. In the wilderness, he tells Rose Marie she was not meant to be confined in a town, and sends her off to be with James.
