Rail-rodents

"Hoiman" and his ratty mice cousins, to escape the winter cold in Brooklyn, hop a streamliner going to Florida. Katnip is also on board and chases the mice from the baggage compartment to the mail car. Herman utilizes very mechanical device available to derail Katnip, and finally uses some war-surplus equipment to shoot Katnip out in space. He lands at the North Pole and is freezing while the mice are living it up on a Miami beach.