After a band of drunken thugs overruns a small Indian Nation town, killing Minister Goodnight and raping the women folk, Eula Goodnight enlists the aid of Marshal Cogburn to hunt them down and bring her father’s killers to justice.

The murder of her father sends a teenage tomboy, Mattie Ross (Kim Darby), on a mission of “justice”, which involves avenging her father’s death. She recruits a tough old marshal, “Rooster” Cogburn (John Wayne), because he has “grit”, and a reputation of getting the job done. The two are joined by a Texas Ranger, La Boeuf (Glen Campbell), who is looking for the same man (Jeff Corey) for a separate murder in Texas. Their odyssey takes them from Fort Smith, Arkansas, deep into the Indian Territory (present day Oklahoma) to find their man.

Following the murder of her father by hired hand Tom Chaney, 14-year-old farm girl Mattie Ross sets out to capture the killer. To aid her, she hires the toughest U.S. Marshal she can find, a man with “true grit,” Reuben J. “Rooster” Cogburn. Mattie insists on accompanying Cogburn, whose drinking, sloth, and generally reprobate character do not augment her faith in him. Against his wishes, she joins him in his trek into the Indian Nations in search of Chaney. They are joined by Texas Ranger LaBoeuf, who wants Chaney for his own purposes. The unlikely trio find danger and adventure on the journey, and each has his or her “grit” tested.