The shroud is slowly slipping from the face of Pretty Little Liars' mysterious murderer.

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Unlike viewers, cast members are already keyed in to 'A's true identity, and Keegan Allen (Toby) believes viewers will be appropriately shocked by the reveal. Set to happen at some point before season 7, the climatic moment will carefully thread back to the early days of Emily, Hanna, Spencer, and Aria's lying spree.

"Everyone will freak out because it's so clearly in every episode," Allen told People. "When it's finally revealed, you could literally go back to season 1 and knowing who it is, you can be like, 'Oh, wow. Whoa. This has been here all along, and I never noticed it,' which is, I think, brilliant."

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There will be some fans that will be able to pull together the teens' complex web of deceit and identify the true culprit in advance. As the impeccably dressed Liars prepare to move on from their bizarre high school careers (how did they ever find time to focus on academia?), series creator Marlene King believes 'A' will reveal him/herself to some eagle-eyed PLL devotes.

"By the end of this season I am sure some people will guess correctly and for the right reasons," King tweeted following season 5's "Fresh Meat."

Find out more when Pretty Little Liars airs Tuesdays at 8 p.m. ET on ABC Family. Click the video below to see a preview for the series' next episode, "Oh, What Hard Luck Stories They All Hand Me."