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 5: "Gamma Zeta Die"? We've gathered our top suspects.

3. Wren Kingston

Why he might be Big "A": Wren is back on our list this week for a couple of reasons. For one, after last week's big confession we're inclined to trust Melissa a tad, so she gets a pass this week. For another, in the "A" tag "A" was drinking tea, and tea is totally associated with Brits, right? But mostly, Wren is the right age to have been potentially hanging around Cicero college back when Ali was calling, so we can't help but wonder if he was involved. After all, we don't know much about what he was up to prior to coming to Rosewood.

Why he might not be Big “A”: As always, we're still lacking a "why" for Wren being Big "A".

2. CeCe Drake

Why she might be Big "A": We've discussed general reasons we're suspicious of CeCe before, and this week left us more suspicious than ever. After all, we know Ali got CeCe kicked out of college, and we can't help but wonder if Cicero was the college in question. We could definitely see CeCe being part of that sorority. Maybe she was the one Ali was calling.

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." That said, we're more convinced than ever that she knows way more than she has let on.

1. Alison DiLaurentis

Why she might be Big "A": Yep, she's still at the top of our list, for all the reasons we've discussed before. And now we know she was calling a random college, adding to the never ending list of mysteries surrounding Ali.

Why she might not be Big “A”: As always, we have to acknowledge that she might actually be dead.

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 16, 2013 at 8 p.m. ET/PT on ABC Family.