An experiment in Russian Alaska goes terribly wrong, with Eddy being engulfed in freezing gases, but results in the creation of a spherical device.

Three years later, Lloyd sends the device, along with its schematics, to his grandson (and Eddy's son), James Ray Steam, who works as a maintenance boy in Manchester, England, along with instructions to guard it.

Ray encounters Lloyd again, who was captured by O'Hara's henchmen, but has escaped from his cell and is attempting to sabotage the castle, revealing that the Foundation's true intentions for the exhibition is to sell weapons of war.

Eager to show the world the castle's true power, Eddy orders it to be prematurely activated, causing the structure to rise and shed its decorative outer shell, revealing it to be a monstrous floating fortress.

As Lloyd and Ray rush to redirect the castle over the Thames, Eddy, whose metal body repelled the gunshot, re-emerges from the steam and assists them, having realized his folly.

The ending montage reveals Ray returning home, and later becoming a global superhero using the jetpack gear from the castle; Lloyd introducing Ray to electricity and finally passing away; Eddy founding a corporate conglomerate; Scarlett maturing and becoming a famous pilot, and a war being fought with paratroopers and zeppelins.

(Development by Cavia and SIMS) Steamboy was released in Japan on July 17, 2004, alongside Pokémon: Destiny Deoxys where it was distributed by Toho.

[10][11] According to the reviewer KJB at IGN this could be due to the marketing methods used and the incredibly small limited release in the United States.

"[13] Metacritic assigned the film a weighted average score of 66 out of 100, based on 32 critics, indicating "generally favorable reviews".

[15] Stephen Hunter of The Washington Post states, "the movie turns out to be one of those science-fiction pieces that is drawn from a peculiar moment in science, so the fiction has a historical sense to it.

Steamboy clearly means to be a critique of Western culture: It uses issues such as industrialism, domination, mass destruction, ambition and despotism as a background to what feels like a boys' book adventure".