We know someone close to the Liars is going to betrAy them in the Pretty Little Liars Season 3 summer finale (Season 3, Episode 12: “The Lady Killer”) by being part of the "A" team.

While we doubt that one of the fab four will backstab the others, this is Rosewood — anything is possible, and the Liars are on ABC Family's suspect tracker. And, after all, what would be more shocking than for one of the Liars to be in league with "A"?

In that spirit, let's look at the possible reasons Spencer (Troian Bellisario) could be the betrAyer.

She's smart enough. Being smart isn't a crime, but being part of the "A" team clearly takes some intelligence, and Spencer has brains to spare. She's definitely clever and ruthless enough to pull off "A" level stunts — if she had a reason to.

Her bad grades. Is this new "A" really so bad that Spencer would be getting Bs and forgetting to apply to college? While the new "A" has upped the ante in some ways, s/he actually tends to be less intrusive, so we're not entirely sure why Spencer has been feeling the pressure so much more this season. Is it because she's leading a double life?

Spencer vs. Ali. We've seen in flashbacks that Spencer and Alison's (Sasha Pieterse) friendship was starting to fall apart just before Ali disappeared. If the "A" team is anti-Ali, perhaps they recruited her that way — though if Spencer has been part of the team all along, you'd have to wonder why Mona (Janel Parrish) was also trying to recruit her. Is it possible that the "A" team has multiple branches that don't all work together?

To protect her family. We find it more likely that if Spencer is somehow involved with "A" team, it's to try and help someone close to her. We know her family has secrets on top of secrets. There's Melissa (Torrey DeVitto) and her fake pregnancy  — not to mention her potential involvement in Ali's death. There's her half-brother, Jason (Drew Van Acker). There's whatever the heck is going on with her mom and Garrett (Yani Gellman). Maybe the "A" team pressured Spencer into helping them in return for keeping her family's many skeletons buried.

To protect Toby? Alternatively, perhaps she decided the only way to help Toby (Keegan Allen) is to join the enemy, perhaps in an attempt to take them down from the inside. That sounds like a very Spencer thing to do, actually.

Troian would like it. On a meta level, we know Troian Bellisario is really into the idea of being part of the "A" team, and it sounds like she's relatively tight with the writers. Is it possible she convinced them that making Spencer part of the "A" team is the way to go?

Let us know what you think in the comments below!

Catch an all-new episode of PLL on Tuesday, August 21 at 8 p.m. ET/PT on ABC Family.

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