This is a John Wayne full length feature which presents John Wayne at his best. Wayne portrays Colonel McNally a Union officer. He befriends two Confederates, Captain Cordona (Jorge Rivero) and Sargeant Phillips (Christopher Mitchum), who are helping him find the people who betrayed his unit. This would be treason, as Union secrets were sold which resulted in the death of McNally's friend. This story is intense. Former Sergeant Ketchum, (Victor French) one of the betrayers settled in Rio Lobo, and has taken over the town by manipulating the sheriff to help him in this task. This has included, unjust incarceration murder and blackmail. Doing this he has been able to acquire most of the town and water rights. Also in the mix, because the Sherriff and his men murdered her friend is Shasta Delaney (Jennifer O'Neal.) She insists on being part of the group who is going to confront the bad guys
This bad blood boils over into a pretty intense gun battle, with a little bit of dynamite thrown in. It also shows that if you hurt enough people, sooner or later they will have their day.
They did something weird with the camera often when changing scenes which was obnoxious.