Denis O'Hare

The list of ghosts on American Horror Story keeps growing. Among the formerly warm bodies we added last week: a woman from the 1920s who coaxed her husband, a doctor with a Frankenstein fetish, into performing abortions on starlets; Moira, who was shot by Constance back when Moira looked like Alexandra Breckenridge; and Hayden, whom Larry murdered because he apparently wants to help Ben not just out of the house but with all of his problems. (Oh come on, you know that's not the last you've seen of her!)

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Unfortunately for the Harmons, Halloween has arrived, the day when the dead are allowed to make like they're living. In the first hour of a two-part Halloween event (Wednesday, 10/9c, FX), series bosses Ryan Murphy and Brad Falchuck are handing out both tricks and treats. Here's what to expect:

TREAT: Infantata, explained! Someone will explain the history of that turn-of-the-century demon baby lurking in the Harmons' basement. Series star Connie Britton told TVGuide.com that it — and she calls it "the Infantata" — just might be the victim of "something really terrible" that happened in the house. That would be an understatement.

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TRICK: The return of Rubber Man — or is it an imposter? Our shiny enigmatic friend will turn up not once, but twice for Halloween. He'll even unmask! But is it the same person donning the gimp suit both times?

TREAT: Vivien's baby checks in! Just like Bella and Edward's fast-growing, gnawing-on-mommy-from-the-inside bundle of joy, Vivien's little guy is going to start demanding some attention in painful ways. (Yes, that is a reference to Twilight. American Horror Story is supposed to be an homage to all things scary, right?) It's only been eight weeks, and the baby should be the size of a peanut, but a super scary ultrasound will show otherwise.

TRICK. Three people will die. So every episode thus far has begun with a murder — the Halloween killings don't all take place in the past.  Death will even claim a pretty major character (who has been in every episode so far) in a pretty gruesome way. In a twist, it will be pretty sad as well...

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TREAT. Hayden isn't over! ...On the other hand, death doesn't mean the end. Just ask Moira. Ben may have built that lovely gazebo over the body of his other baby mama, but on Halloween, the dead get to walk amongst the living. Hayden's pissed and she's going to do a lot more than walk.

Check out a sneak peek from Wednesday's episode. Why does Larry suddenly want money? What does he need that costs a thousand bucks?

American Horror Story airs Wednesdays at 10/9c on FX. The network will air a marathon of the series' first four episodes, starting Monday at 10/9c.

What has been the biggest scare so far? Do you think the Harmons will make it out of that house alive?