Until his death, Sam Kittridge owned owns the Circle K Ranch in Mesa County. Banty Bishop, his foreman, has been working the ranch with Sam for forty years and now has to deal with Sam's inexperienced son Bob from back east. As Banty takes a wagon into town to pick Bob up at the stagecoach station, three masked outlaws men who want the ranch ambush him on the road. When Banty tries without success to draw his gun, one of the outlaws shoots the gun out of his hand and Banty has no choice but to surrender.
In Mesa, Bob arrives by stagecoach and thanks his fellow passenger Red Devers for his advice. Devers offers to work as his foreman but Bob says that he already has one. Bob wonders where Banty is and Devers glances over at two of his thugs, Jake and Sandy. Banty rides into town and tells Bob that the bandits got away with the ranch payroll. Jake steps forward and lies, claiming that he and Sandy saw Banty burying a chest behind the ranch's barn. Bob stands by the foreman but Jake suggests that they ride out to the Circle K and check out his claim. Devers agrees and Bob rides out and digs. They find the chest and Devers points out that bandits wouldn't steal a payroll and then bury it on the owner's property. Bob figures he has no choice but to let Banty go, although he refuses to press charges because he got the money back. Banty says that Sam would know there was a trick going on and leaves, and Bob offers Devers the job of foreman.
The Lone Ranger and Tonto ride into Mesa and see a sign announcing the sale of the Circle K, signed by Devers. The two men know about Devers, who has been running the same scheme to take over ranches in the past under different names. Every time Devers has become the foreman of a ranch, it's put up for sale a few weeks later. The heroes know Bob is a tenderfoot and figure that Devers is taking advantage of his inexperience, tear down the sign, and ride to the Circle K to investigate.
When they arrive at the ranch, the two friends find a drunken Banty beneath a tree, singing to himself. He figures that the Ranger is a bandit and admits that he's out of money and washed up. Banty is glad to let them pitch camp there and the Ranger asks about Devers. He explains that they know Devers is the head of a group of outlaws that take advantage of gullible ranchers. Banty confirms that Devers fired all of the older ranch hands and brought in his own people, and refuses to let anyone near the place. The old timer doesn't care what happens to Bob but figures that he'd never sell the Circle K. Tonto shows him the sign they found and Banty realizes that Devers is forcing Bob to sell.
Tonto disguises the Ranger as an old man and rides into town to get a wagon and different clothing. Once he has what he needs, the disguised Ranger goes to the Circle K and Devers' men draw their guns. The Ranger says he's representing a secret buyer in a neighboring county and they buy his story. Devers agrees to see him and they soon make a deal for the Circle K. As he goes, the Ranger asks for Bob's confirmation and Devers says that Bob will accept the terms. When the Ranger refuses to accept Devers' assurances, Devers claims that Bob had an accident and isn't feeling well but agrees to bring him in.
Devers goes to Bob's room where the bruised and beaten Bob is lying on the bed. The outlaw slaps him around a bit and then tells him to tell the Ranger that he's selling the ranch or else. Devers hauls Bob out and the Easterner tells the Ranger that he just wants to get rid of the ranch at any cost. Once they usher Bob out, the Ranger says that his boss will bring the money in person in four days. When Devers points out that the Ranger's boss wanted his identity to remain a secret, the Ranger says that his boss will wear a mask.
The Ranger goes to where Silver is tied to a tree, removes his disguise and then rides to meet Tonto and Banty. He tells them what happened and assures Banty that Devers needs to keep Bob alive long enough to sign the bill of sale, giving them time to get help. When Banty points out that everyone is scared of Devers, the Ranger asks if the other old timers from the Circle K are scared. Banty assures the Ranger that he can bring a whole legion of them to help and rides off. Once he's gone, Tonto warns that the old timers are no match for Devers' men and the Ranger figures they need to find a way to even the odds.
Banty quickly assembles a group of old timers and brings them back to the Ranger. He tells them to give him and Tonto a ten-minute head start so they can get Bob to safety and then make their move. The Ranger and Tonto then ride to the ranch and Jake and Sandy greet them, figuring the masked man is the mysterious buyer. The thugs greet them and the Ranger goes inside and has Tonto wait. Once Devers has Bob prepare to sign the bill of sale, the Ranger jumps Devers. Devers fires off a shot but Tonto draws a gun on Jake and Sandy.
Inside, the Ranger soon subdues Devers while Bob grabs his gun. Devers warns them that his men will soon come running in response to the gunshot. The outlaws open fire and Tonto ducks inside. Things look hopeless... until Banty and his "Legion of Old Timers" come riding up, guns blazing. Devers figures his men can take care of the has-beens, but the Ranger and Tonto shoot the guns out of the outlaws' hands, evening the odds. Three of the outlaws grab Banty and the Ranger and Tonto loan a helping hand without letting them know so they don't spoil the old timers' fun. The two heroes head out the back way and the Ranger stuns two men from behind. Banty punches them unconscious, unaware of the Ranger's assistance, and goes to find some other opponents. When another outlaw stumbles against a window, Tonto secretly grabs his hand until an old timer knocks him out.
The Ranger and Tonto finally capture the last two outlaws and the old timers tie the bad guys up. Bob comes out and tells Banty that he's back in charge. He wishes he could reward them but Banty assures him that all they want is honest work. Bob assures the foreman that they'll all have work at the Circle K as long as they want it, and says that the same goes for the Ranger and Tonto. As the two men ride off, Banty explains that the masked man was the legendary Lone Ranger and waves to the departing heroes.