Once Upon a Time Preview: Snow White Takes a Dark Turn - Can Prince Charming Save Her?

Once Upon a Time Ginnifer GoodwinGet ready to see a different side of Snow White.

On this Sunday’s Once Upon a Time (ABC, 8/7c), the future princess is out to kill the Evil Queen, and she’s determined to get the job done to an unhealthy degree. But how did the mild-mannered, sweet heroine become a potential murderess?

Not surprisingly the mysterious Rumpelstiltskin is partly to blame. “I didn’t think about the repercussions of taking a potion that would erase the memory of love,” says Ginnifer Goodwin, referring to the concoction Rumple gave Snow to make her forget Prince Charming. “That it would effect you in very logical ways in all aspects of life.”

Turns out that mix Snow drank has made her a little unhinged. “She definitely walks a different road [in this episode],” continues Goodwin.

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With a damaged Snow out on a potentially regretful mission, Charming takes it upon himself to save her from herself and to keep her from ending the Queen’s life. But will he also manage to help his beloved reclaim her memories?

“That’s part of the episode – whether or not that will be addressed,” says Goodwin. Josh Dallas is a bit more reassuring about his alter ego’s efforts, telling TVLine, “He’s doing the best he can to get her to remember.”

“It’s an epic episode with lots of action, and the storytelling is super exciting,” he adds.

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Meanwhile, back in Storybrooke, Kathryn’s disappearance will continue to cast a dark cloud over David and Mary Margaret’s lives. “That’s going to be their new obsession… unfortunately and miserably,” warns Goodwin. Like the potion that took Snow for a dark turn, Kathryn’s case is “going to change” the love birds.

“David and Mary Margaret have this unexplainable draw toward each other, these epic feelings. … But the nature of the curse is that they can’t have their happy ending,” adds Dallas. “I’m afraid the saga continues!”

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Watch Once Upon a Time‘s PaleyFest cast Q&A, hosted by TVLine’s Matt Mitovich: