On the mid-season finale of "Pretty Little Liars," "A"'s threats escalate and the FBI arrives in Rosewood, PA to get to the bottom of Alison's (Sasha Pieterse) murder.

"Is there a level above shocking? That's what it is," Lucy Hale, who plays Aria, tells ET when asked to describe what fans can expect to see.

The FBI is in town when a new piece of evidence turns up, but the girls have all committed to go to Mona's "glamping" [glam camping] birthday party. But then a text arrives that implies that "A" will be at the party, and Spencer (Troian Bellisario) encourages the girls to go because it will be a chance to put an end to the threats.

"One of us knows who 'A' is," Troian tells ET.

"And that girl is going to meet up with the other three and then something crazy and unexpected happens," Lucy says.

The high school students of "Pretty Little Liars" have lots of secrets they are keeping . How Jenna (Tammin Sursok) became blind and what happened the night that Alison went missing are just two. But in real life, both Lucy and Ashley Benson (Hanna) say they aren't big secret keepers. But Shay Mitchell (Emily) tells ET, "I have a couple of secrets that will always remain secrets that I can't ever talk about that I will carry to the grave with me." Sounds like she and Emily have something in common.

The success of "Pretty Little Liars" has resulted in a pickup for 12 more episodes for the second half of the season.

Troian tells ET, "I want to see what happens between Spencer and [her sister] Melissa (Torrey DeVitto) and Melissa and Ian (Ryan Merriman). And then, of course, I want to see how Alex (Diego González) and Spencer turn out because I think they have a good thing going."

It is all about relationships for Shay, too. She says of her lesbian onscreen relationship that she is looking forward to "finding out how Emily deals with everything that is going on within herself and how comfortable  she becomes." But in real life, Shay says it wasn't at all awkward kissing a girl. "I have had other experiences having to kiss a guy and those were really awkward because he was an awkward kisser. Bianca is awesome. It wasn't really awkward at all. When I am in Emily's shoes, I am Emily."

The mid-season finale of "Pretty Little Liars" airs tonight at 8 p.m. on ABC Family.

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