- 1 hr 54 min
The movie surrounds an ex-union officer Col. Cord McNally (John Wayne), who is intent on finding the traitor who sold information to intercept U.S. gold shipments on a train. The betrayal led to the loss of his good friend Lt. Forsythe (Peter Jason). After Forsythe is killed, McNally is captured by confederate hijackers Capt. Pierre Cordona (Jorge Rivero) and his men. Forsythe is able to trick them into going to a Union camp, where Cordona and Sgt Tuscarora Phillips (Christopher Mitchum) are captured. Both men are questioned about the traitors, but claim they only saw them from a distance. McNally asks the duo to contact him through Blackthorne, Texas Sheriff Pat Cronin (Bill Williams) if they ever cross paths with the traitors again. After McNally receives word, he travels to Blackthorne. He is notified by Cronin that one of the men he's looking for is in Rio Lobo. Cordona also tells him that Tuscarora and his father are being bullied by ranchers and could use some help. McNally, Cronin, and a girl named Shasta Delaney (Jennifer O'Neill) head to Rio Lobo. The town is corrupt, lawless and run by Ketchum (Victor French), who hires his own crooked sheriff name "Blue Tom" Hendricks (Mike Henry). After Tuscarora is arrested on bogus charges, the trio go to his father Old Man Phillips (Jack Elam). McNally discovers the traitor is Major Ike Gorman, who is now going by the name of Ketchum. After a standoff, Cordona is captured by Ketcham's men, and Ketchum by McNally. Hendricks slashes the face of Amelita (Sherry Lansing) for helping McNally and Tuscarora; She vows to kill him. Word gets back to several ranchers whose deeds have been stolen by Ketchum. The ranchers ride off to help McNally. After Ketcham's release, he is shot by Hendricks, when he learns that the deeds have been signed back to the ranchers. When the ranchers arrive, Hendricks' men abandon him. Hendrix is gunned down by Maria.