This movie was ten years in the making, and it shows. That's both good and bad. There are lot of threads in the narrative that seemed left over, remnants from earlier versions of the story. Still the animation is amazing and the steam punk is amazingly cool.
It's Victorian England, Grandpa Steam and Father Steam have, while working for the O'Hara company, created the Steamball, a source of nearly limitless steam power and special effects. Now the steamball has been sent to Steam-boy back in england, evil people from the company want it to power their weapons they plan to sell to all comers, Father Steam is blinded by the UNSTOPPABLE POWER OF SCIENCE, Grandpa Steam wants the steamball destroied and Steamboy? He's on the run.