Circa 1873, brothers Dick and Carey Ross evade capture by an American posse by crossing the border into Canada. Later, over a campfire, older brother Dick warns Carey that he will refuse to help if Carey gets them into trouble again. The next day, Carey shoots one of two Sioux Indians who were observing them from afar. The Rosses slip away and end up at Fort Vengeance, home of the newly formed North West Mounted Police. Dick insists that they join up with the NWMP despite Carey’s protests against the military lifestyle. During their interview with chief inspector Maj. Trevett, Dick admits that they fled Dakota due to a gunfight provoked by charges that Carey was cheating at cards. Dick maintains, however, that they do not have criminal records. The brothers successfully complete training with other new recruits and they all become constables. When Chief Sitting Bull enters Canada with his tribe after the massacre at Little Big Horn, Trevett is instructed to prevent him from waging war. Sitting Bull consults with Blackfoot chief Crowfoot and urges him to join forces against the whites, but Crowfoot refuses, remaining loyal to the Queen. Trevett leads a NWMP troop to the Blackfoot encampment to welcome Sitting Bull and the meeting is peaceful. Later, however, Sitting Bull orders Broken Lance, a member of the Sioux tribe, to attack white settlers in order to incite a war, but insists that his son Blue Cloud wait to avenge the death of his brother, the Sioux killed by Carey. Sitting Bull’s plan to place blame for the raids on the Blackfoot tribe backfires after Dick and Trevett identify the arrows as Sioux. After the NWMP are called to defend a wagon train that is under attack by the Sioux, Dick chases Broken Lance from there to Crowfoot’s encampment. Based on the evidence of the arrows, Crowfoot allows Dick to arrest Broken Lance, and the Indian is found guilty and hanged. Sitting Bull then plans to declare war but is thwarted by Crowfoot, who refuses to allow his people to fight. Carey, meanwhile, slips back into his wild ways and one afternoon, makes a secret deal with trader Francois Luboc to sell pelts stolen from a hidden Indian cache. When Crowfoot’s son Eagle Heart reports the theft of his pelts, the Rosses are assigned to find the culprit. After Eagle Heart confirms that the pelts sold to trading post owner Patrick Fitzgibbon bear his mark, Fitzgibbon identifies Luboc as the trader. Carey volunteers to arrest Luboc and finds him at his cabin, held at gunpoint by Eagle Heart. During a gunfight with Eagle Heart, Carey kills Luboc and escapes, leaving behind his riderless horse to give the appearance that he has died. Constable Macrae, who was sent to help Carey, arrests Eagle Heart for the murders of Luboc and Carey. Suspicious of the circumstances, Dick searches for his brother and finds his uniform hidden under the floorboards of Luboc’s cabin. After obtaining a fresh horse from Fitzgibbon, Dick sets out again, unaware that he is being followed by a vengeful Blue Cloud. Crowfoot, meanwhile, agrees to ally with Sitting Bull if Eagle Heart does not receive a fair trial. Dick finally tracks down Carey, after which his brother admits his involvement with Luboc. When Dick insists that Carey turn himself in in order to avert a war, Carey refuses and attacks him. Blue Cloud observes the struggle and kills Carey. Although he mourns the loss of his brother, Dick realizes that Blue Cloud saved his life. They return together to the fort in time to prevent Eagle Heart’s hanging and stop a joint attack by the tribes of Crowfoot and Sitting Bull. Eagle Heart is then released and peace is restored.