Johnny Mack Brown rides into town to discover his horse that was stolen from him. Entering the saloon, the thief identifies himself and tries to sell Johnny's horse back to him that earns the thief a beating. Witness Chet Norman explains to Sheriff Dave that Johnny was in the right. Chet wishes to use Johnny's skills to stop a series of stagecoach holdups that is bankrupting Chet, the owner of the state line. Each of the robberies takes place in the Whistling Hills with the survivors of the robbery swearing they heard a whistling signal.
