Though Mona Vanderwaal (Janel Parrish, 23) is currently locked up in a mental hospital, the girls of Pretty Little Liars are still being tormented by the mysterious "A."

In a sneak preview from Tuesday's all-new episode, Emily Fields (Shay Mitchell, 25) freaks out when she's given a necklace made of human teeth. "I can't breathe," she says after receiving the jewelry from "A."

As Hanna Marin (Ashley Benson, 22) and Spencer Hastings (Troian Bellisario, 26) debate whether it's actually made of human teeth, Aria Montgomery (Lucy Hale, 22) reminds her pals that their problems extend far beyond a creepy necklace.

"Guys, real or not, this 'A' is working overtime to frame us," she tells them. "We keep digging ourselves in deeper."

Pretty Little Liars airs Tuesday at 8 p.m. EST on ABC Family.