Pony Post is about that fabled if short lived Pony Express which carried mail to and from the west in 1860. Johnny Mack Brown takes over a troubled express station because the former manager Stanley Blystone has used the place to cover a lot of his gambling debts.When Brown fires Blystone, Blystone starts getting into all kinds of criminal activities in uneasy partnership with brothers Ray Teal and Jack Rockwell.Two women vie for Brown's attention. One is Nell O'Day whose father's horse ranch supplies a lot of the mounts for the riders. The other is Dorothy Short whose father Tom Chatterton is the big boss of the Pony Express who put Brown in charge.Lots of criminal activity, suspected double crossing, and enough riding and shooting for any front row kid. Together with the comedy and comic songs of Fuzzy Knight who is the horse wrangler at the station but wants to be a rider. He even invents a trampoline like device for easy mounting. You have to see how that works out.