Every 'Pretty Little Liars' A.D. Theory Ranked From Best To Worst

We're sooooo close to finally finding out all the truth behind all those mysteries on Pretty Little Liars, and as we get closer to Tuesday's series finale, the one question on every fan's mind is the same: Who is A.D.?

The show's biggest mystery has plagued fans all season, as we keep getting so teasingly close to figuring out who's behind all the torture in the Liars' lives, only to get thrown off yet again. Of course, there are still a good amount of fan theories about A.D. that could hold up in the finale.

Some theories are more convincing than others, but in the end, any of these people could wind up being A.D.... or none of them could be! Let's break down some of the most likely theories about who is actually A.D.:

1. Ezra

Probably the most convincing A.D. theory points to none other than Ezra as the secret mastermind. Fans have pointed out A.D. has known things about Aria only Ezra could know, and the way A.D. has blackmailed Aria could actually be a twisted test of loyalty for Ezra.

Plus, there was that note from A.D. in the last episode that just read "Time for pie," and the character most associated with pie has always been Ezra.

2. Melissa

Another popular theory suggests Melissa is A.D. This theory stems from the fact the season has been planting seeds of her connection to Charlotte all along, and it would make sense she's the only one actually upset after Charlotte's death and might create this blackmail game to avenge her.

3. Caleb

One shocking theory makes a good case for Caleb to secretly be A.D. Since Caleb does have a shady past, and we know he's great with technology, everything about him could add up to be A.D. The theory suggests Caleb is actually Charles, and he's really much older than he's told everyone on the show.

4. Spencer's twin

And let's not forget the popular theory A.D. is a character we've never met before... even though we may have basically seen her. One of the big theories online is A.D. is actually Spencer's long-lost twin sister.

This one mostly goes back to the scene early on in the season when Hanna is being held captive by A.D., and "dreams" Spencer is with her. Some fans don't believe that was a dream at all, and that Spencer's twin was indeed there with Hanna.

5. Mona

Though this theory has kind of fallen by the wayside in the latest episode, for a while it seemed like Mona was definitely going to be revealed as A.D. in the finale. She's been a mastermind messing with the girls' lives before, and it really looked like she was at it again, but actually, she was only the person behind Charlotte's murder, and apparently nothing else. But then again, you can never be too sure.