'Pretty Little Liars' Halloween Special Tonight, Oct. 22 Watch Here (VIDEO) 

"Pretty Little Liars" anticipated Halloween special is supposed to be full of twists and a huge reveal when it airs tonight. 

Executive producer Marlene King said, "There is a huge reveal that changes the series to where we can never turn back."

Producer Oliver Goldstick told HollywoodLife.com that "the four girls come out of this episode with a whole new plan of attack."

Alison could possibly return, which brings out strong emotions in Spencer. 

"We knew there would be backlash," Oliver tells us. "But when you look back, a lot of things will make sense; we try to make it not so out-of-the-blue. We have dropped clues. We plant things that will pay off in a awesome way!"

"Spencer will take things into complete overdrive this year," Troian Bellisario tells us. "Spencer becomes obsessed in a new way, and she takes on unhealthy habits to take over the investigation herself. [This special is] going to open a few more interesting secrets that nobody was ever aware of."