In 1885, three mismatched frontiersmen (teacher Riel, whiskey trader Corbeau, and trapper Duroc) foment rebellion in central Canada; only the local Mounties stand in their way. Constable Ronnie Logan loves Corbeau's savage daughter Louvette; his pal Jim Brett loves April, the district nurse, but finds a rival in visitor Dusty Rivers, a Texas Ranger who wants Corbeau for murder. Treachery, battle, and tense situations follow in rapid order, with more lighthearted intervals.

In the Canadian Northwest of 1885, whiskey runner Jacques Corbeau recruits schoolteacher Louis Riel to lead a revolt of half-breeds against the encroaching settlement of the white people who are being protected by the Royal Canadian Mounted Police. Meanwhile, at the fort feelings run strong between Corbeau's hot-blooded young daughter Louvette and Constable Ronnie Logan, and Logan's sister April, a government nurse and Sergeant Jim Brett. Into this tense situation rides Dusty Rivers, a Texas Ranger on the trail of Jacques Corbeau, who is wanted for murder in Texas. A rivalry develops between Jim and Dusty over April, but after the half-breeds steal a Gattling gun, the differences between the two men are forgotten as Dusty escorts April to safety at Batoche, the rebel capital, while Jim rides to the Indian camp to prevent Corbeau from inciting the Indians to war. At Batoche, Riel sends Dusty into a trap at the Indian camp where the half-breed convinces Chief Big Bear to go on the warpath in return for the uniforms of the redcoats whom he will kill. Meanwhile, Ronnie and Constable Jerry Moore ride to Duck Lake to protect the 10,000 rounds of ammunition that the panicky settlers have left behind. When one of April's grateful Indian patients warns the nurse that the half-breeds are planning a massacre at Duck Lake, April begs Louvette to sneak through the lines and warn Ronnie. Instead, Louvette tricks Ronnie into deserting his post and holds him captive while his friends are killed. After the massacre, Jim orders Dusty to accompany April and the wounded to the river and await reinforcements while he rides with his six remaining men to quell the Indian uprising. Arriving just as Corbeau is bragging about his massacre of the redcoats, Jim's appearance causes the chief to call off the war, and Jim arrests Corbeau. Once the reinforcements arrive, Dusty rides off to destroy the Gattling gun and locate the missing Ronnie. Finding the disconsolate Ronnie in Louvette's tent, Dusty convinces him to return and face punishment. An angry Louvette pays an Indian to kill Dusty, whom he calls "the white man on the horse," but when Ronnie rides off on Dusty's horse, he dies in the lawman's stead. Dusty takes Ronnie's body back to the fort, arriving just in time to give credit to Ronnie for destroying the Gattling gun, thus exonerating the dead soldier's name. With peace restored, Dusty tricks Corbeau and takes him back to Texas to stand trial, and Jim settles down with April.