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 8: "The Guilty Girl's Handbook"? We've gathered our top suspects.

3. Ezra Fitz

Why he might be Big "A": As we've explored before, this theory isn't totally without merit, and last night's episode reminded us why we've sometimes been sceptical of Aria's love. The fact that Ezra seems so interested in the Liars even while broken up with Aria gives us pause. Sure, he's probably just helping Emily because he's nice and still cares about Aria (and by extension, her friends), but he was prying an awful lot. Plus, wouldn't it be kind of brilliant if he intentionally pushed Emily to reconnect with her volunteering roots in a purposeful attempt to destabilize her family even more?

Why he might not be Big “A”: Calm down, Ezrians. We have a hard time imagining the writers actually going in this direction. As far as we know he has no reason to torture the girls or care about Alison (unless he was Ali's beach hottie?), and we get the feeling the writers are too invested in the Ezria relationship to make Ezra truly evil.

2. Wren Kingston

Why he might be Big "A": Wren hasn't been in this season, but that doesn't mean Rosewood's hottest and most suspicious doctor has been far from our minds. Now that we know someone associated with Radley paid Wilden off to cover the truth about Toby's mom, we can't help but put our focus on Wren again. Sure, he's a bit young to have been working at Radley at the time but a) We don't really know what his backstory is, and b) It's possible he wasn't involved with Toby's mom's death, but started using the sordid tale to blackmail Wilden and anyone else involved. That might help explain the intense tension between he and Eddie, and why Eddie seemed so freaked out when Spencer started asking questions.

Plus, his absence so far this season makes him more suspicious, rather than less. We have no idea where he's been, and the answer could be running around Rosewood, pulling strings and torturing the Liars.

Why he might not be Big “A”: As always, we have to wonder why Wren would spend so much time tormenting teen girls. Was he involved with Ali before she died? Is he trying to cover up (or even uncover) something about her death? Is he just a psychopath with a thing for teen girls? So far, we don't know enough about his life before the premiere to have any idea about what his motivation could be.

1. Alison DiLaurentis ... or Her Twin

Why she might be Big "A": Ali is at the top of our list for all the reasons we've discussed before, but this week we want to float the twin theory again, too (sure, the writers said they aren't exploring it, but we still think it's an interesting idea). Now that we know Wilden has been doing dirty deeds since at least the time of Toby's mother's death, we can't help but wonder if that's how he and Ali first became intertwined. If Alison did have a twin and either the real Ali or the evil twin were at Radley, she could be responsible for Ms. Cavanaugh's downfall. Or maybe not — maybe she just knew the truth about Ms. Cavanaugh, and that's why she was targeted in the first place. Either way, it could lead to a lot of explanations.

Why she might not be Big “A”: As always, we have to acknowledge that Ali might actually be dead, and the writers do say they aren't going to explore the twin thing on the show.

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, August 6, 2013 at 8 p.m. ET/PT on ABC Family.