Fancy a trip to the dentist? You might rethink the visit once you’ve seen the Canadian promo for Season 4, Episode 17 (“Bite Your Tongue”) of Pretty Little Liars. Also explored in the tantalizing new trailer: Aria’s loathing of Mona; Alison in her element; and Emily on the attack...

“I was at the dentist and I think I got treated by ‘A,’” a freaked out Hanna tells the other Liars. We’d say her suspicions are right, based on the later shot of Spencer pulling a message from one of her crowns. Does health insurance cover note-by-tooth procedures? “Who is this monster?” Aria asks, in exasperation. If only you know, Aria.

Elsewhere in the promo, Emily is having some super creepy times. We see her wandering through the darkened halls of Rosewood High, and she seems to think she’s not alone. “I need you to come to the school and pick me up,” she frantically tells someone over the phone. But Em’s troubles don’t end there. Later in the promo, she is in a darkened house (basically, she spends this entire episode in the dark), and someone still seems to be after her. She hides next to the door as it swings open, some sort of makeshift weapon in hand, not waiting to see who it is before she attacks.

Spencer seems to be in full-on sleuth mode in next week’s episode. We see her looking over the photos she took of Ali’s diary pages before it was stolen. “I’m trying to piece this together,” she says in voiceover. Cut to a shot of Alison looking like her flashback self. “I don’t know why I’m taking advice from someone who doesn’t know how to order,” she says with sass. Is this a memory Spencer is reading from Ali’s diary, or is Alison back for next week’s ep? We’re leaning towards the former.

Meanwhile, Aria is casting stink eyes at Mona. “Mona’s the devil,” she says, followed by a shot of Mona flirting with a high school boy. Is that Mike she’s talking to? Because that would be such a Mona move and we know she’s getting a new love interest this season. Drama!

Which storyline are you most looking forward to? Sound off in the comments below!

Catch the next episode of Pretty Little Liars on Tuesday, January 28, 2014 at 8 p.m. ET on ABC Family.