On the second half of Pretty Little Liars season 4, some of the girls will not be so happy to find out that Alison (Sasha Pieterse) is alive.

In the latest Pretty Little Liars Halloween special, the girls discovered that Alison, the friend they thought was dead, was actually alive. Alison will make her big return a few episodes into the second half of season 4, and not everyone is thrilled about it.

"There's going to be a really interesting dynamic because Alison didn't leave on the best note," Pieterse told TV Guide recently. "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."

Pretty Little Liars Spoilers: Jason DiLaurentis & Noel Kahn Return and 'Move Things Forward' 

Fans can rest assured that a lot of story lines will be resolved in the upcoming episodes of season 4, including many details on what Alison had been doing all this time while the girls thought she was dead.

"There is a lot of resolving going on this season," Pieterse said. "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."

Pretty Little Liars Season 4 Winter Premiere [PHOTOS] 

Pretty Little Liars returns for its season 4 winter premiere on Tuesday at 8 p.m. on ABC Family.

Watch a promo for the Pretty Little Liars winter premiere here: