Credit: Adam Rose/ABC Family Channel © 2012 Disney ABC Television Group Photo: Spencer and Her Dad at the Dance in Pretty Little Liars Season 2, Episode 22

We all want to know who "A" is on Pretty Little Liars, but an equally intriguing mystery is the identity of Alison's (Sasha Pieterse) killer — after all, "A" and the murderer definitely don't have to be the same person.

We've been wary of Spencer's (Troian Bellisario) dad, Peter Hastings, for a while now, and a new sneak peek of Season 2, Episode 22: “Father Knows Best” is setting off major new alarm bells.

We've taken a look back at all the clues that make us very suspicious that Peter was involved with Alison's untimely death.

He's morally flexible: Back in Season 1, Mr. Hastings told Spencer not to fess up to plagiarism, because he thought her reputation (and the reputation of the family) was more important than doing the right thing. While stealing your sister's paper is nothing like murder, this may have been an early clue that Peter's priorities are seriously screwed up.

The hockey stick: The first moment we became super suspicious of Papa Hastings was during Season 2, Episode 7: "Surface Tension," when he freaked out at Toby (Keegan Allen) just for digging up Melissa's (Torrey DeVitto) old field hockey stick. He didn't help his case by burning the stick while making crazy eyes and ranting. Even more damning? The stick may have belonged to Melissa, but apparently Ali had borrowed it, which means it could have been a very convenient weapon. Is it possible the shovel isn't the only thing that hit Ali that night? 

The Jason factor: Peter didn't seem to have a real motive for killing Alison until we learned that he is Jason's (Drew Van Acker) father in Season 2, Episode 19: "The Naked Truth"and Ali knew. Would he resort to murder to keep his secret safe?

Blackmail? His potential motive gets even stronger if Ali really was blackmailing him. He denied that she was very fervently, but then again, if he killed her for it, of course he would deny it.

Melissa's suspicion: In this new sneak peek for Season 2, Episode 22: “Father Knows Best,” Melissa (Torrey DeVitto) admits to Spencer that she also has a bad feeling about their father. Apparently Peter had a "really weird reaction" to hearing about Ali's death, as if he was "relived." Hmmm...

It would be heartbreaking: Producer Lisa Cochran-Neilan says the finale will be "heartbreaking," and according to Ian Harding (Ezra Fitz), the revelation of "A"'s identity won't be the most shocking thing that happens in the episode. Finding out Peter was the killer would be surprising and heartbreaking.

In fact, the main thing that makes us think Peter isn't the killer is that it almost feels too obvious.

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