When potential settlers in the territory of New Mexico are harassed by cattle rustlers, Governor Lew Wallace sends deputy sheriff John Steele to straighten out the problem. John quickly discovers that the leader of the rustlers is Sam Crew, who poses as a prosperous business man. John pretends to be a drunken drifter in order to secretly watch Crew. Crew welcomes a group of settlers that includes Ginger Malloy, her small brother Pat and her uncle, Cal Brett, but later sends his men to steal their cattle. During a gunfight between the settlers and the bandits, a rival gang led by Sonora Joe steals the cattle and Cal is killed. With the help of his horse "Duke," John retrieves the cattle and enlists Sonora's help against Crew. He announces that, as deputy sheriff, he will arrest Arizona, Cal's killer, precisely at nine o'clock, and with Sonora's help, he does. The gang plans to rescue Arizona when he is transferred to the fort for trial, but John uses a ruse to thwart their plans. Meanwhile, the settlers drive their cattle to the fort where they plan to sell them, and Crew decides to stampede their cattle drive. John once again rescues the cattle, and Crew is trampled to death by the herd. Now that Crew is gone, the settlers can live peacefully, and John and Ginger plan to marry.