Has the excitement of Phoebe Tonkin joining The Vampire Diaries worn off at all yet? No?

You may continue celebrating, but do so with this warning: things are about to turn awfully dark in Mystic Falls.

That's what producer Julie Plec teased during an interview at this month's CBS Television Critics Association All-Star Party, cryptically saying of early episodes:

The Vampire Diaries Season 4 Trailer 

The Vampire Diaries Season 4 Trailer

There is an overreaching arc of evil, and this year, we're doing something a little different in that we don't know or say who that is right away. The mystery is who is this evil because clearly it's something or somebody, and we don't know who it is. And so that's a question we'll be asking a lot in the first few episodes as we build up to our first... reveal of the season's bad guy.

We presume Plec is referring to the vampire hunter to be portrayed by Todd Williams. But it sounds like there will be a lot going on outside of this one new Mystic Fall resident, doesn't there?

Ponder the possibilities now and head over to Wetpaint to read the full interview with Plec.