You are Corvo Attano, royal protector to the unmarried Empress Jessamine Kaldwin and her daughter Emily. It is immediately apparent that extreme care and effort went into the setting of Dunwall, a fantastical city overrun by a rat-spread plague, but it's not like the city of Rapture was to BioShock. BioShock fully explores the story of Rapture, it is the story of Rapture. Dishonored, on the other hand, is not the story of Dunwall - it is merely set there.
There are many elements emphasized regarding life in Dunwall, but hardly any of them are explored in this specific story. It creates a bit of dissonance over time, since set pieces and locales you'd swear should be included are not. This is all to say that Dishonored is the very specific story of Corvo Attano and his reaction to the conspiracy against Empress Kaldwin.
Gallery: Dishonored (4/26/12)