Pretty Little Liars fans are in for a special treat next month:
The ABC Family smash, which doesn't return with new episodes that truly tie in to ongoing storylines until 2012, will air an October 19 Halloween installment titled "The First Secret." It will take viewers back to the time soon before Alison went missing.
Look for "a new girl in town to challenge Ali for Queen Bee dominance," according to the official network description, and for Aria to learn a "shocking revelation" about her father in this unique flashback episode. Below, we've posted a handful of photos from the upcoming hour. Click through them now to see everyone in costume: