The new poster for Boardwalk Empire offers some advice: know who's behind you. This is particularly good advice in Nucky Thompson's case, judging from the ominous paranoia that so infused the recent trailer. So, who could be coming up behind Nucky this year? How about crime lord rival Rothstein? Or government agent Van Alden? Heck, maybe the gatling-gun crazy KKK, from the trailer? We won't find out the answer until season two of Boardwalk Empire premieres on September 25, but in the mean time, at least we'll be able to marvel at the gorgeous period outfits. So many waistcoats, so little time.