A mysterious killer has ambushed and killed nine people in the Robbers' Roost country of Utah. Wyatt's old Army friend, Colonel Benteen, begs him to take the case so that the cavalry may be saved in the event of an Apache attack. And before Wyatt is through he has to enlist the aid of every notorious outlaw in Robbers' Roost to get the mysterious killer and those behind him.

In his most energetic disguise, that of a cowhand, Wyatt Earp is after the murderer of a cousin and joins a cattle outfit coming up the Chisholm Trail. The Outfit is commanded by a devious tyrant who has unique punishments for those who offend him. Wyatt, suspecting him early, is put through a tough time.

Earp and Judge Tobin are forced to enforce a rustling law they think is too strict. A group of five ranchers have filed a complaint against another rancher but all of them have been guilty. Even Shotgun Gibbs is accused of stealing Roscoe.

Again Wyatt Earp meets his friend Ned Buntline and Mr. Buntline has just published a book describing Wyatt as the King of the Frontier without realizing the embarrassment to which such stuff will subject Wyatt. Embarrassment it is when Wyatt is forced to enter a rodeo to prove that Mr. Buntline is no liar and the big feature is a ""shootout"" at two hundred yards, between Wyatt and his Buntline Special and an enemy with a Winchester.

Wyatt's younger brother, Morgan Earp, visits Dodge City and is immediately involved with Doc Holliday in a scheme to rescue the outlaw Smiley Dunlap, who is being held prisoner by Greg Norton and his gang. Wyatt's task of saving Morgan and Doc from being killed is made harder by his desire to keep his little brother from knowing he had a hand in rescuing the rescuers.

Doc Holliday is very sick with his wife Kate threatening to leave him since he won't follow anyone's instructions to get better. Earp convinces him he should reform to keep Kate. The reformed Doc with no liquor and guns keeps Earp busy.