Orphan Tetsuro desperately wants to exchange his boyish body for a mechanical one, as many on his planet have already done, and seek revenge on Count Mecha - a cyborg who killed his mother. To achieve this, the boy tries to steal a pass for the Galaxy Express 999 from a lady at the station, which travels to the necessary planets. Tetsuro's theft attracts the wrath of the entire police force, but luckily the lady helps him and gives him the coveted ticket. And so Tetsuro sets off towards his dream, encountering various adventures along the way.