James a hidden armory filled with massive steam-powered war machines built by Eddy, and James struggles with the moral dichotomy of being a scientist - of how to contribute to the world without giving into vanity, leaving him conflicted as to whether to side with Lloyd or Edward, who themselves have become estranged. Lloyd and James reach the core of the castle and remove one of the Steam Balls, but Lloyd is shot and recaptured by O'Hara, as James escapes with the device. The next morning, the exhibition is underway, and James brings the ball to Stephenson, giving him the ball and the knowledge he acquired in captivity. The British military attempts to arrest Eddy, but Eddy unleashes his steam powered weapons on the soldiers, turning the exhibition into a battlefield. When Stephenson uses the Steam Ball to enhance his own company's tanks, James realizes that he had no better intentions than the Foundation. 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 the Royal Navy and Stephenson attempt to defend London from the floating fortress, James steals the Steam Ball back and uses it to create a makeshift aircraft to re-board the fortress. James meets Eddy, Scarlett, and Lloyd in the castle's control room, where Lloyd confronts Eddy about his actions, before shooting him in a fit of rage, but Eddy falls into a cloud of steam and disappears. With the castle steered off course, the structure has become unstable and threatens to explode over the city. As Lloyd and James 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. James re-installs the stolen steam ball, and makes his way to the control room to make a final escape with Scarlett on an emergency jetpack, while Eddy and Lloyd reconcile and halt the machine over the river and escape as well. The castle detonates in a spectacular explosion, sparing the city from destruction. The ending montage reveals James returning home, and later becoming a global superhero using the jetpack gear from the castle; Lloyd introducing James to electricity and finally passing away; Eddy founding a corporate conglomerate; Scarlett maturing and becoming a famous pilot, and