True Grit is an adventure story.
Portis’ novel is narrated in the first person by Mattie Ross, a thrifty, churchgoing spinster distinguished by a rare independence and strength of mind. In keeping with Mattie's worldview, the story is replete with Biblical motifs, especially the “eye for an eye” style of justice. As an old woman in the year 1928, she tells the story of her adventures many years earlier, when, at the age of fourteen, she undertook a quest to avenge her father’s death at the hands of a drifter named Tom Chaney.
Joining Mattie in her quest are Rooster Cogburn, a one-eyed U.S. Marshall hired by Mattie because she considers him to be a man of true grit, and a Texas Ranger named LaBoeuf who is also tracking Chaney for a murder in Texas. The two men try hard to leave Mattie behind, but she proves more tenacious and resourceful than they'd expected and eventually she becomes an accepted member of the posse.
Together, but with very different motivations, the three ride into the wilderness of the Oklahoma Territory to confront Ned Pepper's gang, harboring Chaney. Along the way, they each exhibit their own grit in a tale that explores the themes of justice, vengence, and redemption.