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 the Season 4 premiere (Season 4, Episode 1: "'A' Is for A-l-i-v-e")? We've gathered our top suspects.

3. CeCe Drake.

Why she might be Big "A": CeCe was Ali's evil bitch Jedi master, so we know she has the right temperament. Ali told her all of the Liars' secrets, so it's possible Ali dished about Toby's mom as well, which would explain "A"'s texts to him this week. CeCe looks enough like Alison that combining her figure and hair with an Ali mask makes her a more believable fake Ali than most other characters. In fact, maybe she doesn't need the mask — Mona claims she thought CeCe was Ali when CeCe visited her in Radley. Now that Wilden's dead, she's more suspicious than ever — they clashed in Season 3, she "left town," and now he turns up murdered? Yeah, we haven't forgotten about you, Ms. Drake.

Why she might not be Big “A”: The biggest reason we think it's probably not CeCe is meta one: She didn't show up until Season 3. We kind of doubt the writers would make such an important villain someone we didn't even hear about until so late in the show. It feels a bit like cheating. Plus, we still don't have a good reason for CeCe to target the Liars.

2. Melissa Hastings

Why she might be Big "A": She's always been suspicious, she has plenty of motive to hate Ali, Spencer, and by extension the other Liars, and she's always disappearing at convenient times (like right now). She's a Hastings, so clearly she's crazy smart. On the Season 4 premiere, Mona dished that Shana and Jenna are scared of Melissa — and anyone who can scare Jenna has to be one bad mofo. Yes, in the Season 3 finale it was implied that Melissa was part of a separate group that fans are calling the "B" team, but we wouldn't put it past her to play both sides for her own ends. Plus, someone started deleting Mona's files just before the Liars could see if the second Queen of Hearts was Melissa. Coincidence? 

Why she might not be Big “A”: There have been enough sisterly moments between Melissa and Spencer that we have a hard time imagining Melissa trying to truly ruin Spencer's life. Exact some revenge? Sure. But frame her for murder, the way it looks like "A" is doing with the Liars and Wilden? We're less convinced. Plus, is it just us, or does Red Coat's complexion not really match Melissa's?

1. Alison DiLaurentis

Why she might be Big "A": Masks, shmasks. The Liars haven't been seeing a creepy doll face of Alison during their supposed hallucinations, they've been seeing Alison. Not to mention that Ali is totally the kind of person who would wear a mask of her own face to disguise her identity. She's still the person with the easiest access to the Liars' secrets (and, after tonight, we also know she knows more about Toby and his mom than most people) and the easiest excuse for being wherever she wants whenever she wants (if people think you're dead, you don't even have to answer for your whereabouts). She's one of the few characters who comes off as twisted enough to mastermind all of "A"'s evil doings. Plus, sometimes it seems like "A" is sorta kinda helping the Liars, and vacillating between real moments of kindness and extreme cruelty is totally Ali's MO.

Wilden's death is just more evidence in Ali's favor. As we learned last season, they have a history, and as Jenna pointed out in the premiere, he saw Ali the night she died (or "died," if this theory is true). That's two reasons she might want him dead; perhaps she's the one who killed him.

Why she might not be Big “A”: Well, there is the little matter of her being dead. Maybe medical records don't lie in this case. And we do know someone tried and almost succeeded at killing her, so she's not all powerful.

Of course, these aren't the only people we have our eyes on (where are you, Wren? Enquiring minds are always suspicious). 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.