River's End (1940)

Convicted murderer John Keith (Dennis Morgan), escapes from his guards, and is pursued by Sergeant Conniston (Dennis Morgan, of the Royal Canadian Mounted Police. After a two year hunt, Conniston almost dies of the cold and is rescued by Keith. Before he dies, Keith convinces him he is innocent of the crime for which he has been convicted, and Conniston insists that Keith, who bears nearly an identical resemblance to the Mountie, put on his uniform and pretend he is Conniston and go to River's End and prove his innocence.