In the distant future, humanity has found a way to live forever by purchasing mechanical bodies, but this way to immortality is extraordinarily expensive. An impoverished boy, Tetsurou Hoshino, desires to purchase a pass on the Galaxy Express 999—a train that travels throughout the universe—because it is said that at the end of the line, those aboard can obtain a mechanical body for free. When Tetsurous mother is gunned down by the villainous machine-man hybrid Count Mecha, however, all seems lost.