It's the beginning of the end.
Judging from the terrifying teaser, it appears that Mona is being confined in an isolation cell, away from the rest of the Liars. Why is A separating Mona? Our guess is that he's punishing her for conspiring with Hanna, Spencer, Aria and Emily in the season five finale. And A's punishment may result in death. At 0:10, "M" (for Mona, probably) has left the Liars an ominous message: "He's going to kill me." Yikes.
Never fear, it's Officer Toby to the rescue! At 0:12, it looks like Toby has somehow found his way into A's dollhouse -- and he's got a gun. If there's one thing we've learned from watching five seasons of "PLL," it's that guns and Liars just don't mix. Someone always ends up getting shot, and we doubt it's going to be Charles this time around.
That being said, is Toby alone? Or did he bring the force with him? Now that Detective Tanner seems to be on the Liars' side, we'd hope she'd send backup for Toby. We wouldn't mind seeing Toby and Caleb team up to take down A, though.
We also see Ali sneaking around A's dollhouse in that infamous yellow shirt, which we hope is a flashback because there's no one Ali snuck out of prison... until Tanner is using her as bait? It's possible Ali knew Mona was alive the entire time, which seems more likely.
But perhaps the biggest surprise is Aria's hair. First of all, who cut it? Did she cut her own hair in protest of A? And secondly, where the eff did she get pink hair dye? How did all of these physical changes happen in a matter of hours?! Curse you A, and your cruel mind games.
We have no idea how the Liars are going to get themselves out of A's dollhouse, but when they inevitably do, it looks like they're leaving poor Mona behind. We are NOT okay with this, Marlene King.