Entitled, "400 Days," it's a single episode that follows five different survivors at different points through a 400 day period.
You can check out the official trailer here or below:
According to the official FAQ, this episode will make reference to your past saves, and will also influence the upcoming Season 2.
What concerns me, of course, is the game breaking bug that's preventing me from completing my third playthrough on my Xbox 360. If I get this episode and the same "HDD has been detached" error keeps happening, I'll have wasted my Microsoft Points as Telltale Games has officially told me they don't have a solution for me at this time.