Sasha Pieterse Sasha Pieterse

Pretty Little Liars' Alison DiLaurentis is officially alive.

During the show's annual Halloween special, fans' suspicions were confirmed when Alison (Sasha Pieterse) suddenly revealed herself to the girls in Ravenswood. But their reunion was short-lived when Alison gave a quick warning about someone she's terrified of and then disappeared. Before Aria (Lucy Hale), Spencer (Troian Bellisario), Emily (Shay Mitchell) and Hanna (Ashley Benson) could ask questions they were left in the dark dying to find out, among many things, who has been tormenting their friend, why she can't come home yet and if she wasn't the girl that got buried, then who was?

"There is a lot of resolving going on this season," Pieterse tells "Now you see the other side of it and you'll find out why she didn't go to the police or her parents. You have to figure that something really bad had to have happened for her to stay away from everyone. The interesting thing is also why she's revealing herself now to the girls."

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On the premiere of the second half of Season 4 (Tuesday, 8/7c, ABC Family), the girls try to figure out who's buried in Alison's grave, while also reconciling with the fact that their former best friend is truly alive.  But don't expect to see Ali show her face again just yet, in fact you might have to wait a few episodes for another reunion. When she does pop up, not everyone is excited. "There's going to be a really interesting dynamic because Alison didn't leave on the best note," Pieterse says. "Considering a lot of what the girls have been through, the fact that she was alive and didn't do anything will have a big impact on them. I really like the first time you see me alive again, it's a special moment, but you'll also be so pissed off at a character."

With A always setting his or her target on someone, Pieterse says that both Spencer and Aria will get hit the hardest this time around. "Spencer and Alison have always butt heads because they're so much alike and when Spencer follows a trail she follows it hard and she goes through a lot of devastating things — she goes down a really dark path," Pieterse says. Could this have to do with her suspecting Ezra (Ian Harding) as A? "Aria doesn't know anything about Ezra, but [Spencer] senses it already. But here's the thing about Ezra — even if he isn't A there's something really fishy going on. So no matter what Ezra and Aria's relationship will suffer."

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What about the other members of the A-Team or Alison's "helpers"? "You will see Mona again," Pieterse says. "The real great thing is everything connects and so if you re-watch you'll find little pieces. If you re-watch the episode where Mona tells Hanna that she saw Alison in Vivian Darkbloom mode that is a clue. And you had CeCe (Vanessa Ray) pretending to be Alison in her red coat so there are little clues in there. Alison has helpers and for significant reasons Alison knew a few characters before the girls even did and those were her safe places in the most unexpected ways."

Looking back at Alison's rocky journey, Pieterse says she believes her character ultimately has a good heart — despite what we've seen from her. "She's gone through a lot," Pieterse says. "That's not necessarily an excuse. She's very manipulative, but she used to thrive on knowing people's secrets because that was her only way to have something against them and that was something she learned from a young age. It became second nature to her. In a weird way when it comes to the four girls she was trying to get them to be honest. The only reason she had something on them was because they were being sneaky! So I do think she has a good heart and she's changed. She wants a second chance."

Watch a sneak peek at the premiere below:

Pretty Little Liars returns on Tuesday at 8/7c on ABC Family.