Near the Canadian-American border, Indian agent Roy Rogers joins the Oseka Indians in celebrating the return of the salmon to spawn. As part of the festivities, Roy competes against several Royal Canadian Mounted Policemen in the tribe's annual horseback race. Later, a fish cannery owner named Banning, and his foreman, Stagg, visit Oseka Chief Nogura to explain their plans to build a new cannery on the river. Nogura tries to reason with them, saying that his people have barely enough to eat as it is, without the added competition of another cannery. Later, a field nurse named Ann Keith tells Roy that the entire Oseka tribe is in danger of starving if their situation does not improve. When Roy meets with American government official Henry Gates, he learns that the government is considering forcing the tribe onto a reservation. Later, Nogura's son Dacona jumps onto the back of Banning's cannery wagon and begins knocking crates off onto the road. Stagg then grabs Dacona, ties him to the back of the wagon and drags him. When Roy witnesses this, he jumps aboard and begins punching Stagg in the face. Later, Banning agrees to let more fish reach the Indians if they, in turn, will promise to quit sabotaging the cannery. Later, Nogura tells Roy that his fishermen found a dead Mountie in the river some time ago. A mark on his neck seemed to indicate that the Mountie had been strangled before being dumped into the river. As he was running from the river, Nogura explains, he dropped his rifle and now fears being accused of the crime. Soon, Mounties arrive to search the Indian village for Nogura, while the real culprit, Stagg, who had killed the Mountie while trying to burn down the competing Canadian cannery, is free from suspicion. Later, when Deputy Bill Hartley captures Nogura, he is turned over to Roy's custody. On Roy's urging, Nogura returns to his village, where he is promptly arrested by Sheriff Bradley. When Roy meets Mountie Sgt. Douglas, he urges him to work toward a salmon fishing agreement which all parties must honor. While the Indian braves clamor for war, Roy goes to the jail to visit Nogura and realizes that he has been kidnapped. Guessing that Banning is responsible, Roy and his friend Splinters break into his office. After the gang arrives and Roy rescues Nogura, he determines that the mark left on Nogura's neck by Stagg's whip is identical to the one found on the dead Mountie. When Roy learns that the gang has set several burning rafts drifting toward the Canadian cannery, he rushes to extinguish the flames. Roy then captures Stagg, using his own whip to lasso him from his horse. After Roy delivers Stagg and Banning to the Mounties, the Indians once again celebrate the river's teeming salmon population.