In 1874, after their father is wounded by hard men who have stolen a number of mares and Smokey, a prized stallion, sixteen-year-old Rob McCann and his adopted Native brother, Luke, ride frantically to Fort Ellice, Manitoba, in the vain expectation that the horse rustlers have stopped there. Learning that a new force called the North-West Mounted Police has come west, the brothers continue south to locate them and ask for help.

The NWMP commander, Colonel George French, desperately attempts to have the boys escorted home. However, the brothers manage to tag along on the...