 The third entry in the Hopalong Cassidy films finds Jim Arnold (Howard Lang),owner of the SV Ranch, writing and asking for Hopalong Cassidy (William Boyd)to aid in the struggle against a gang of rustlers, led by a man known only as Nevada.Arnold also asks that Cassidy NOT bring his friend Johnny Nelson (Jimmy Ellison), as Arnold wishes to cool down the romance between his daughter Margaret (Jean Rouverol) and Johnny. Cassidy takes along Bar 20 hand Red Connors (Frank McGlynn, Jr.), which hacks Johnny off as usual and the hothead storms off making plans of his own.While Cassidy waits in the hills for a meeting with Arnold, Johnny arrives at the SV and encounters a rival for Margaret, George Perdue (Harry Worth), a cultured,snuff-sniffing dandy---real wsterners dip---who, is in reality Nevada, a man with a Napoleonic complex, who plans his cattle raids on the tatics used by Napoleon in his military campaigns (other than Waterloo), and he rules his men with an iron discipline. Meanwhile, Cassidy appears at the ranch posing as a dude, and with the help of an old prospector known as Windy (George Hayes, long before he became George "Gabby" Hayes), begins an investigation. Cassidy, who could out-dude anybody when he chose to(and he often chose to and often to the dismay of Cassidy fans)soon discovers that Perdue and Nevada are one and the same. With a pre-arranged signal from Cassidy, the ranchers, led by Johnny, Red and Arnold, sweep in and wipe out the rustlers.