How did we not know?!?

As seen in this Vampire Diaries clip, this is the reaction most of Elena's friends will have on Thursday when they learn that their pal has actually been Katherine for a number of weeks now.

But Damon? His initial response will be a nod of respect to his nemesis for pulling off such a con... even if it did lead him on a killing spree.

Watch Damon be told about Katherine's reception in the following sneak peek from The Vampire Diaries Season 5 Episode 15 and watch Stefan tell his brother not t worry. Everything is under control.

Is it really, though? We somehow doubt it.

Go watch The Vampire Diaries online if you need a refresher and get an early look at "Gone Girl" via the following photos:

The Vampire Diaries Photos from "Gone Girl"

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Matt Richenthal is the Editor in Chief of TV Fanatic. Follow him on Twitter and on Google+.