In 1878, Dodge City, Kansas, is a dangerous place to live. When six-year-old Cole Herbert wakes one morning to find his mother, Katherine, missing and his father, Clint, out riding posse with Wyatt Earp and Bat Masterson, he realizes just how dangerous it is.
Clint and Cole embark on a mission to find Katherine, but after an unsuccessful, eight-month search, they find their way to the Oklahoma Territory, where they plan to begin a new, more secure life. As years pass, father and son adjust to life on a small ranch. But when an old prospector knocks on their door and informs them that Katherine may have been spotted alive in the Arizona Territory, they revive their search and head to Waterhole, the small, gold-mining town where Katherine may be located.
Waterhole, Arizona, is home to Sal Gregorio, the ruthless town leader, who is not willing to share any of his information or his town with the Herberts. When Sal interferes with their attempt to leave town after realizing that he poses a definite threat to their lives, Clint and Cole must devise a plan to get everyone in their party-including a wounded man, a trusted friend, a drug addict, a stranger, and a pre-adolescent boy-out of town alive.