'Supernatural': Eve meets Sam and Dean -- but what's her endgame?

In Friday's episode of "Supernatural," the Winchester Brothers will finally come face to face with Eve, the Mother of All. Though she's usually played by guest star Julia Maxwell, the villain will take on a different face this time -- she'll look like Mary (Samantha Smith), the boys' long-dead mother.

"It's not really Mary, and Sam and Dean know that. [She thinks] she'll be easier for the boys to talk to this way," executive producer Bob Singer tells Zap2it. "She thinks they can be persuaded because he is her mother."

Luckily, Sam and Dean have had their mother's image used against them before -- Zachariah fully creeped us out when he told them he'd been hooking up with her in Heaven in Season 5.

Eve's motivations remain a bit of a mystery as the season draws to a close. "She's here for a reason. Her kingdom is being messed with. If Crowley's running hell, and Cas is having a war in heaven, she's really the mother of purgatory and all those monster souls that go there. She's unhappy. Her children have been tampered with and in her mind she's being a good mother to them."

Catch the next new episode of "Supernatural" Friday night at 9 p.m. EST on The CW.