Major Randolph McIvor's son Lin helps train his horses and his other son Sandy rides them. Their stable has fallen on hard times, but they are preparing their promising new thoroughbreds Encino and Tarzana for the
Kentucky Derby. Lin is in love with Armistead's daughter Pat, although her wealth intimidates him. Armistead has a star horse called Blue Grass that also will be a Kentucky Derby contender. No one but Pat knows that Blue Grass's sire was a different horse than the one that had been originally intended. A trainer named Layton files a formal complaint after Blue Grass wins the Kentucky Derby, claiming that the winner's pedigree can not be proven. However, he is fired and Pat agrees to marry Lin. ==Cast==