I'll leave the plot synopsis to other reviewers. Certainly this film is well worth the watch for anyone with an appetite for quality hand-drawn animation (mixed almost flawlessly with some nice 3D effects). Unfortunately it falls short in the presentation of its story. The steampunk setting is interesting enough, to be sure, but the novelty of this sci-fi / Industrial Age environment can only carry the viewer for so long.
Frankly I was getting bored stiff about halfway through it. It's not that the plot doesn't have developed characters, histories, motivations, etc...it's just that the writing, or maybe the storyboarding, was so poorly done that there is simply no build and release of suspense, no ebb and flow or calm before the storm or anything like that. It all just kind of plays out at a constant level of semi-frantic conflict that tires itself out long before the climax. It's a shame, too, considering the originality of the story and the unbelievable amount of care that went into this film's creation.
Perhaps it's worth a look just for the visuals. Otherwise I'd say it's just one of those movies you might consider watching if you have nothing else to do.