Exclusive American Horror Story Video: Ben's Ex Is Back -- and She's a Real Nightmare!

A new form of terror is about to invade American Horror Story‘s spooky abode.

In next Wednesday’s episode of the FX thriller, Ben’s pregnant mistress Hayden (24‘s Kate Mara) pays an unexpected visit to the Harmon’s new home — and TVLine has an exclusive first look at the character’s frantic and unhinged arrival.

“She’s completely unbalanced,” says co-creator Brad Falchuk. “She can say all she wants about being over him, but she’s unbalanced. And he’s in real trouble.”

Check out the clip below and then hit the comments with an answer to this question: What’s scarier — that house or crazy-ass Hayden?

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