Alison's mysterious Pretty Little Liars' helper is a little too close to home for Aria's comfort.

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Little Mike Montgomery (Cody Christian) is all grown up and harboring murderous secrets. The Liars were busy worrying the Holbrook (Sean Faris) problem like a loose tooth, but instead of finally yanking that sucker, the Liars realized another culprit was lurking just off their radar.

Aria's (Lucy Hale) younger brother reveled his entanglement in Rosewood's deadly games during "Oh, What Hard Luck Stories They All Hand Me," and it appears Mike's involvement is far from over.

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"[Next weeks episode is] going to be a big one, I'll tell you that, it's gonna be a big one," Christian told People of "Out, Damned Spot." "I think that next week the fans are going to see a much darker side to Mike that's going to raise much more suspicion, and we're going to be asking so many questions. I mean, you just want to know what's going on with the character and why he's doing the things that he's doing. But, ultimately, we will get the answers by the finale, and we're going to see how all of his behaviors are justified - or not justified, for that matter."

What will Mike get up to next? 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.