Kevin can't believe that the Pony Express was able to deliver the mail without any help from mail trucks or airplanes! At the National Postal Museum, Kevin watches a video on Warren "Boston" Upson, the most daring Pony Express rider. Through the power of his imagination Kevin takes a fantasy field trip and rides Boston's perilous mail route. The Civil War has just begun, and Kevin must get word to Sacramento. Can Kevin overcome bandits, wolves and snowstorms to deliver the news?