Rio Conchos is a story about two men who won't let go and keep seeking vengeance. Richard Boone is a former Confederate soldier who came home to find his family massacred and is wreaking a terrible vengeance on the Indians. Kind of like Ethan Edwards would in The Searchers if left to his own devices.
The other man is Edmond O'Brien, Boone's former commanding officer, who is seeking vengeance for the lost Confederate cause and the way it went down in Generals Grant and Sherman's war of attrition. He's hijacked a group of repeating Spencer rifles and is about to trade them to Chief Rudolfo Acosta of the Apaches.
When Boone is found with one of the repeaters by the army, he's tossed in the guardhouse and then given a choice of staying there or leading Captain Stuart Whitman to the weapons. After thinking it over somewhat Boone agrees.
So an unlikely quartet of Whitman, Boone, Jim Brown, and Anthony Franciosa set out. This group has little regard for each other and that does impede the teamwork involved to successfully pull off the mission of either get the weapons back or destroy them.
This was the feature film debut of Cleveland Browns halfback Jim Brown who went on to a pretty successful acting career after his days on the gridiron were through. OF course Tony Franciosa as their Mexican guide/interpreter is as usual the best one in the film. Talk about someone no better than he ought to be.
Rio Conchos has enough action to satisfy the biggest western fans around. The ending, shall we say the conclusion of the film and the mission leave an uncertain future for the survivors of the last battle.