Credit: ABC Family

Big "A". Red Coat. The evil head honcho. Whatever you call this twisted guy or gal, 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 10: "The Mirror Has Three Faces"? We've gathered our top suspects.

3. Mrs. DiLaurentis

Why she might be Big "A": There is something seriously off about Ali's mom, and we can't help but wonder if her obsession with Ali goes beyond the understandable inability of a mother to move on from her daughter's tragic murder. For instance, could she be running around town in an Ali mask, torturing Ali's old friends (who she very well could blame for Ali's death)? It's not outside the realm of possibility. After Episode 10 we know Mrs. DiLaurentis is associated with Radley, and, honestly, we're not 100 percent sold on her story about why she knows the doctor. It's possible she was a patient there.

Even if not, her response to Ali and CeCe's prank was very harsh — as Ali complained, she almost slammed the piano lid down on her daughter's fingers. Could that be a hint that Mrs. DiLaurentis is dangerous?

Why she might not be Big “A”: While Mrs. D technically has been a character since the first season, she was MIA for most of the series. It would be a little weird, pacing wise, for her to come back and be revealed as the Big Bad after being gone for long. Plus, she seems to really appreciate the girls being around, which would run counter to her blaming them for Ali's death.

2. Wren Kingston

Why he might be Big "A": Let us count the ways. This ever-suspicious doc just got ten times sketchier last night, making sketchy phone calls, scoping out Hanna, and going head-to-head with Mona, who thinks he has the wrong loyalties and is keeping secrets. At this point, it's hard to believe he's not up to something.

Why he might not be Big “A”: On top of still not having a clear motivation to be Big "A", after last night we feel more like Wren is answering to someone else — quite possibly Red Coat, but maybe not — than that he's in charge. Mona prodded him about his loyalties, and he seemed almost subservient on his final phone call. As we said, we're pretty convinced something is up with him, but we're not quite sure he's running around Rosewood in Red.

1. Alison DiLaurentis

Why she might be Big "A": As always, Ali is one of our top suspects. And hey! Last night we got confirmation that she plays the piano (like "A") and everything. And her mom "saw" her, just like the Liars! Plus, what was the deal with that whole "switching personalities" with CeCe thing? We're not quite sure, but it's the latest on the long list of reasons to think Ali is capable of just about anything.

Why she might not be Big “A”:  First of all, she could really be dead. Second of all, at this point it might be too obvious. Perhaps Ali being alive really is a red (ha!) herring.

Of course, these are hardly our only suspects. CeCe, for instance, has now been given extra motivation, and is clearly highly suspicious — in fact, the only reason she's not on our list is she seems too obvious. However, this is 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 20, 2013 at 8 p.m. ET/PT on ABC Family.