The Main Event (movie, 1938)

FBI agent Mac Richards takes his girlfriend, Helen Phillips, to a world championship boxing match only to learn that the event has been canceled because the titleholder has been kidnapped. Mac is entrusted with the ransom money, but the kidnappers discover that his fellow agents have surrounded the train station locker where the money was to be dropped and order the champ's manager to have the money delivered by an usher to a different location. With Helen disguised as the usher and Mac driving a cab, the pair set off to deliver the money. The gang isn't taking any chances, though - they waylay the cab and take both the ransom money and Helen to their hideout. Now Mac and his fellow agents must rescue both the champ and his sweetheart before they come to harm.