Casey's employer, the Midwest & Central Railroad faces bankruptcy unless it gets a U.S. mail contract for the St. Louis to Ft. Worth run. The catch is that the company that gets the contract must win a train race. The MCRR's track runs through the Ozarks, but Casey still thinks his engine, the Cannonball, is faster than his competitor's, but the Southern & Panhandle Railroad, the rival company, sends saboteurs and gunmen to slow his progress.