After the Cherokee Strip is opened to homesteaders, Milt Dawson is unable to sway his son John's desire to work on a trail herd. John loves Hanna Lewis, but has been hired to lead a group of settlers from Kansas through Indian territory back to Frontier, Oklahoma. Frontier's vice activities are controlled by Ace Holmes, who plans to drive away the locals and sell their property to newcomers for a profit. After Ace kills peace-loving Bert Sawyer, Hanna's father Tom urges the citizens to hire a sheriff. Milt accepts the position reluctantly, and after he warns Ace to change his ways, Ace shoots him in the back. On the trail, John's wagon train is attacked by outlaw Kit and his gang, who are looking for food and gold. John makes peace with the outlaws by agreeing to drop off a supply of food. When John arrives in Frontier, he is dismayed by the news of his father's murder, and then takes on the sheriff's responsibilities. John orders Ace to close his establishments by six o'clock that evening. Ace tries to trick John into an ambush by sending a note to John that directs him to his father's killer. On the way to the meeting place, however, John recognizes Ace's gang's tracks and disarms their sentry, Pete. John puts Pete on his steed and the man is shot to death as John escapes. John returns to town to close down the saloon, but the bartender knocks him unconscious. However, before Ace is able to kill John, Kit and his men arrive, and when John regains consciousness, he makes Kit's gang deputies. After Ace summons the Norton gang, Tom joins the fight and sets fire to the saloon. John, meanwhile, is trapped between Ace's and Norton's men. As Kit shoots and kills Ace, he is killed by Ace's bullets. Later, the local minister asks his congregation to remember the people who fought lawlessness, and John and Hanna listen together.