After Wyatt Earp's (Henry Fonda) brother James is murdered by cattle rustlers, the frontier legend becomes Tombstone's marshal and sets out to avenge the younger man's death. Torn between his badge and his fury, Earp confronts the likely killers, the notorious lawless family of Old Man Clanton (Walter Brennan), setting the for the famed shootout at the O.K. Corral. Along the way, Earp falls in love with a schoolteacher named Clementine (Cathy Downs) which also pits him against the cantankerous Doc Holiday...