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 4: "Face Time"? We've gathered our top suspects.

3. CeCe Drake.

Why she might be Big "A": We've discussed general reasons we're suspicious of CeCe before, and this week raised some red flags again. Given how close they seemed to be the summer before she disappeared, we can't help but wonder if CeCe was the one driving the car Ali sped off in during the flashback. Plus, there's the fact that Melissa claims Wilden was following someone's orders. Who do we know who was a) connected to Wilden, b) smart and ruthless enough to find a way to control him? We can really only think of two people: CeCe and Ali.

Why she might not be Big “A”: As we've said before, we can't really imagine a character who joined the show so late in the game being Big "A"  — but we do think she probably knows a lot about what happened that summer.

2. Alison's Theoretical Twin

Why she might be Big "A": We haven't brought up the "Ali has a secret twin, and that twin is eeeeevil" theory in a while, but after last night, we feel the need to mention it again. Why? Two things. First is the suggestion that Toby's mom was being bothered in Radley by a blonde with bad juju. This was obviously supposed to make us think of Ali, but what if it was actually her twin? One theory is that Ali's twin was locked away in Radley for a while before escaping to wreak havoc; if the twin does exist and really is crazy evil, she could be responsible for killing Toby's mom. The second thing we noticed is that Ali seemed scared in the flashback this week, not at all the in-control girl we know. Could she have been running from her crazed sister?

Why she might not be Big “A”: Well, for one thing, the show has yet to give us any definitive evidence that Ali actually had a twin, and the executive producers have suggested that's not the route the show is going. It's hard for a twin to be "A" if that twin doesn't exist!

1. Alison DiLaurentis

Why she might be Big "A": Yep, she's still at the top of our list. And really, this week just added to reasons to be suspicious. Ali's desperate need for cash in the flashback could easily be because she was going underground. The fact that Toby's mom was being bothered by a blonde did make us think of Ali. There's the Wilden thing we mentioned above. Plus, the very fact that Melissa, too, thinks Ali might be alive adds weight to that theory. And, of course, there are all the reasons we've discussed before.

Why she might not be Big “A”: First off, as always we have to acknowledge that she might be dead. And not just that! As we said above, in the flashback Ali seemed scared. While we remain pretty convinced she's alive (maybe just because we really want it to be true), we should acknowledge the possibility that, rather than being Big "A", she was also on the run from "A" (whether that's her twin or not).

Of course, these aren't the only people we have our eyes on. 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, July 9, 2013 at 8 p.m. ET/PT on ABC Family.