The Pretty Little Liars Season 4 summer finale (Season 4, Episode 12: “Now You See Me, Now You Don’t”) took us inside "A's” lair, and we're pretty sure there's no better place to find answers than the main baddy's headquarters.

So, what can we learn from what was shown in "A’s” lair? We've gone back over the episode to break down everything that was in this mysterious room.

Giant photos of Ali. One thing's for sure — "A" is definitely obsessed with Ali. He has giant photos of her adorning the walls. Talk about creepy! There is also an album full of photos of Ali, including ones where she was wearing a shirt she bought for a date with an "older guy." It also includes a letter from Ali to the boy in question where she lied and said she was 18; it indicates she met the guy in question in Rosewood.

Boards tracking the Liars. Obviously, "A" has been keeping meticulous track of all of the Liars' movements, as evidenced by the boards that are full of their pictures and details about their lives. Some notable takeaways are that "A" had pics of Wren, and a note saying "Wren at Radley." Does that mean Wren's not on the "A" team?

Boards tracking Ali. There are similar boards tracking Ali. What clues can we learn from them? Here are some takeaways:

  • Ali had a Vivian Darkbloom driver's license, registered in Philadelphia.

  • "A" knows about Ali's possible pregnancy.

  • Is Ali still alive? The boards sure suggests so. They include an image of Red Coat and a picture of Ms. Grunwald. It suggests she was at the lodge the night of the fire, and seems to indicate she's in Ravenswood now.

Diary? The lair also includes a book that looks like a diary; Hanna grabbed it, and we're guessing it will give us a lot of clues and maybe even some answers down the line.

Photos of every relevant person. One wall is covered with basic headshots of almost every person who's ever been on the show, or so it seems.

Event posters. Another wall is decorated with posters from all sorts of events around town.

The computer setup of doom. One section of the lair is dominated by a complex computer setup and a series of maps; as far as the Liars can tell, this is how "A" spies on them everywhere they go.

"A's” bank account. Spencer stumbles on evidence that "A" has formed a corporation. In it, there are two payments made to CeCe from the week prior. The company is also named after Ali's favorite beach in Cape May.

The black suits. Can't forget the closet full of black suits, which suggests "A" is a guy!

Creepy gas mask costume. Why does "A" have this? Other than to give us nightmares, of course.

Is Ali going to be at the party? Perhaps the most important clue of all: Ravenswood is having a celebration that night, and "A" thinks Ali is going to be there.

What did you learn from "A"'s lair? Sound off in the comments below!

Find more Pretty Little Liars spoilers here.

Catch the Pretty Little Liars Season 4 Halloween special on Tuesday, October 22, 2013 at 8 p.m. ET/PT on ABC Family.