Rex Allen, Slim Pickens and the Rhythm Riders, ranch hands employed by wealthy Arizona grandee Carlos Alvarez all lose their jobs because of ranch foreman Link Felton, who has planned what he believes to be the perfect crime and wants a clear field. He knows that on a certain date the Comanche Limited will be carrying a million dollars in gold on a return trip from Chicago. He has found a hidden spur track leading off the main line into an abandoned mine tunnel only a few miles from the Alvarez hacienda. He plans to hi-jack the train, run it into the tunnel, blow up the end of the tunnel, and when the excitement of the missing train has died down, to dig out the gold. The fate of the entombed passengers concerns him none at all. Alvarez is having troubles with his granddaughter Lita who has fallen in love with Rodney Brewster, a Chicago actor and fortune hunter. Alvarez, in Chicago to break up this romance, returns on the doomed Comanche Limited. But, upset by his quarrel with Lita, he gets off the train at a way station and joins Rex and his friends on a three-week cattle drive. Felton steals the train, Brewster moves in to collect on Lita's inheritance (since the missing Alvarez is presumed dead), and Rex has a lot of work to do before everything is solved and straightened out.