Five years after the Big A reveal, several things have changed in Rosewood. For example, Radley has been turned into a stylish hotel and, for unclear reasons, people don't seem the least bit creeped out by the idea of sipping martinis in a building with a super shady past. But, plenty of things remain the same — the police department is as incompetent as ever, the Liars have yet to learn that funerals don't double as fashion shows, and Mona is still suspicious on Pretty Little Liars.
Mona's not to be trusted and our first clue was that Hanna seems to have an axe to grind with her former friend. Prior to the time jump, they appeared to have made amends and Hanna had forgiven Mona for everything she put her through. We learned during the "5 Years Forward" special that the two even went on spring break together during college — perhaps something happened during or after that trip that caused Hanna to mistrust Mona again.
But, most importantly, at the end of the March 1 episode "Burn This" it was heavily implied that Mona is the one who called Charlotte on the night of her murder. Although this doesn't automatically make her the killer (because that would be way too simple), it does mean that Mona is once again up to no good.
Here are four theories about what the original A may be up to in Season 6B:
1. Lucas & Mona Are Working Together
I'm a big fan of the theory that Lucas is the new Big Bad who is "hiding in plain sight." We know that he assisted Mona when she was A, so maybe she's returning the favor — or he's blackmailed her into helping him. Mona did a top-notch, creepy job of playing the A game, so Lucas would be wise to recruit her. And, if she was unwilling to rejoin the game, he has a whole lot of dirt on her that could destroy her political aspirations — especially if he knows that Mona is the one who attacked Bethany with a shovel on Rosewood's most deadly night.
2. She Called Charlotte To Make A Deal
After Mona did a 180 with her testimony only for Charlotte to turn up dead, she immediately shot to the top of my suspect list because I figured she'd decided to take justice into her own hands. But, now she seems like too obvious of a suspect for the murder itself. In the Season 6A finale, Mona stayed behind when the Liars left the tech lair — and we still haven't received an explanation why.
Since she essentially handed over all the A game intel to Charlotte during her time at Radley, Mona may have simply wanted to meet up with her that night in order to make sure they'd reached a détente and they could both move on with their lives. After Charlotte's murder, it makes sense that Mona wouldn't want anyone to know she'd spoken to her that night — like Aria, she would have known that she'd automatically become a suspect.
3. She Got The First Text From The New Big Bad
If Peter Hastings is to be believed, the Liars weren't the first ones to get creepy texts from the new Big Bad. It's possible the new A sent Mona a threatening message on the night of Charlotte's release, prompting her to believe her former tormentor was after her again. Mona's not exactly the type to sit back and let that happen, so she called Charlotte to confront her about it. Again, this doesn't mean she's the killer — but it definitely makes her look suspicious.
4. Mike Killed Charlotte & She's Covering For Him
Mike's conspicuous absence has made him a prime suspect in Charlotte's murder — after all, she victimized both his girlfriend and his sister. If he is truly the killer, I doubt Mona would turn him in, so her sketchy behavior could be related to the fact that she's helping cover up a murder. And, although Mona as the sole killer seems too simple for Pretty Little Liars, it's possible that Mike and Mona conspired to murder Charlotte. She could have called Charlotte in order to lure her to the church where Mike was waiting to kill her.
Mona wouldn't be Mona if she wasn't hiding something sinister — but we'll just have to wait to find out exactly what her secret is this time around.
For more theories, check out Bustle's PLL podcast, Taking This One To The Grave.