I'll start give Dishonored the highest praise I can offer - it reminds me of Thief. Sadly though it's not as good, but then again what is?
You play Corvo another mute protagonist from a long line of mute protagonists, wrongly convicted of the murder of the empress, imprisoned, escaped, and seeking to restore the rightful heir to the throne. All set against a steampunkish victoriana industrial setting with magic. It's a little Thief 2 ish with camera-type sentries and roving guards some encased in stilt-walkers all the while sneaking around to get to the goal; knocking out guards, hiding bodies, and picking up loot. That's if you want to, nothing wrong per se in killing all the guards and charging through. Well nothing overtly wrong but doing so will result in the 'bad' chaos ending.
The influences are clear mostly Thief 2, a dash of Bioshock 2 and a light brush with Assassin's Creed. So inevitably I'm going to be comparing this to Thief 2 so if you haven't played this game - what the hell is wrong with you! Go, buy it now it's dirt cheap and play it, then play it again on the hardest setting now come back after the week it's taken you.