Pierre of the Plains.

In the Canadian Northwest, Royal Mounted Sergeant Tom Redding courts Jen Galbraith. Jen dislikes her brother Val’s friend Pierre, calling him "The Devil". Val takes offense when an Indian states his love for Jen, killing him. When Tom stops to visit Jen enroute to deliver secret orders to Fort Desire Pierre drugs the Mountie's coffee because he fears he carries a warrant for Val’s arrest. So, he does and after Val is arrested Jen and Pierre help him escape. An enemy tries to thwart them, but fate intervenes, and Pierre and Jen finally acknowledge their love for each other.