The Unbroken Promise (1919)

Nell Loring, a Texas sheep rancher's daughter, stops a fight between her father and his neighbor John Corliss, a cattleman, who have feuded for years. Although John loves Nell, he keeps it secret when she promises to marry his errant brother Billy if he stops drinking. After John rescues Nell from a runaway horse, though, she confesses that she really loves him. Worried about the feud, Nell makes John promise never to kill anyone. After Billy is wounded in a barroom brawl, John refuses him money until he reforms. Angered, Billy plots with Fadeaway, a cowboy John dismissed, to rob John's safe. John remembers his promise during his subsequent fight with Fadeaway and only punches him soundly. After Fadeaway is killed by the sister of a woman he betrayed, John, believing that Nell killed him, plants evidence to convict himself. Although Billy, now reformed, tries to take the blame, the murderer's written confession frees John to marry Nell.