Credit: ABC Family

Big "A". Red Coat. The sicko in charge of it all. Whatever you want to call her (or possibly him), the Liars' greatest threat is still a mystery on Pretty Little Liars, which means every episode is a new piece of the puzzle. Who do we think "A" could be after Season 4, Episode 2: "Turn of the Shoe"? We've gathered our top suspects.

3. Wren Kingston

Why he might be Big "A": "A" gave Toby important info about his mother ... from Radley's files. Assuming the files are the real deal, that puts Wren back on our watch list in a big way, since, as a doctor at Radley, he'd have easier access to the files than just about anyone. Combine that with his marginally creepy obsession with the Liars (yes, Spencer is amazing and Hanna is great, but why can't this hot doc find a girlfriend his own age?), and we have to continue to question what the heck is up with him.  

Why he might not be Big “A”: We've yet to discover a compelling reason for Wren to be involved in such a big way. Is it possible he was the mysterious "beach hottie"? There hasn't been evidence pointing in that direction, but since we know very little about Wren's history before the show started, there's not really anything to rule it out, either. That would certainly be a big twist! And if the beach hottie is Big "A", that would explain why he knew not to answer his phone.

2. CeCe Drake.

Why she might be Big "A": The amount of emphasis put on what went down at Cape May in this episode makes us even more suspicious of Ali's beach buddie, whose mean girl manipulations and physical resemblance to her mentee in bitchiness already made her a top suspect. If the parrot knows secrets from that summer, CeCe is definitely someone who might not want it to talk. Plus, we know she visited Mona in Radley. Could she have tracked down the files on Toby's mom then, too?

Why she might not be Big “A”: As we've said before, we're not convinced that the writers would make CeCe Big "A", because she didn't show up until Season 3. Shouldn't such a big villain have been around since Season 1?

1. Alison DiLaurentis

Why she might be Big "A": Let's be real: Until we get definitive proof that she's dead, Ali is going to remain at (or at least near) the top of our "A" suspect list, for all the reasons we've discussed before. And this week only added to the evidence that Red Coat is really Ali. For one thing, we learned that she had a habit of holding her breath for a long time to piss off her mom, which could explain how she managed to survive being buried alive. We also had Ms. DiLaurentis saying she didn't look at Ali's remains, which could be a clue that she wasn't really the one who was killed. Plus, if the parrot really did know Ali's secrets (such as that potentially important phone number), it would make sense that she'd want it out of the Liars' hands.

Why she might not be Big “A”: As always, there's the fact that she's, you know, dead. It's only the incompetence and/or corruption of basically every professional adult in Rosewood that makes the medical report on her death unreliable, but it's possible that in this case, someone got something right.

Of course, these aren't the only people we have our eyes on (mysteriously missing Melissa is still high on our watch list). In Rosewood, anything is possible!

Who do you think "A" is? Sound off in the comments below!

Catch the next episode of Pretty Little Liars on Tuesday, June 18, 2013 at 8 p.m. ET/PT on ABC Family.