Emilie de Ravin and Robert Carlyle, Once Upon A Time

If you thought Once Upon a Time's take on Beauty and the Beast would stay completely true to the whimsical, dark fairytale, Lost's Emilie de Ravin has a few words for you: "There's no singing and we don't have any dancing clocks or anything either."

Exclusive: Once Upon a Time Casts Lost's Emilie de Ravin as Belle

In Sunday's episode (8/7c, ABC), the actress who once donned a shaggy wig and toted a crazy-looking squirrel baby around in the final season of ABC's island mystery series will transform into Belle, an often odd and bookish young lady who's unaware of her true beauty. And just like with the other Disney princesses who've made their way to the series, Once takes a more mature, adult approach in depicting Belle.

"She's actually quite a grounded young woman," de Ravin says. "She still wants to not just do what's expected of a woman in fairy tale land, which is basically to just stay in the castle, marry Gaston [Sage Brocklebank], probably have a bunch of children and all that."

When her family is faced with an ultimatum — Rumplestiltskin (Robert Carlyle) will save their kingdom in exchange for Belle — she decides to go with him. "It's always been her dream to be the brave one," de Ravin explains. "In this scenario, it's to save her family and make a sacrifice. She loves her father, and more than anyone, she wants to save him; in a different way [than] the original story, but still in essence."

De Ravin's beauty will then try to tame the beast. In this case, the heartless and conniving Rumplestiltskin is the savage. "It goes from being his captive to her being out and about in the castle, being more relaxed around him," de Ravin says. "She begins to realize that he's not that scary of a guy, he just thinks he is. There is actually a different side to him, which scares him when he sees her realizing that. He's not used to letting his guard down whatsoever. He has no belief that anyone would like him, let alone love him or actually care for him.

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"They both start changing," she continues. "She becomes more interested in helping him to realize that he is this really cool, interesting guy and he gives her a little more confidence in the situation that she's in — that maybe it's not so bad when she thought it was going to be a pretty awful experience."

Just don't expect a happily ever after. At least not yet. (De Ravin will return in a later episode to continue Belle's story.) "Things don't always end up happy with a dance or a song," de Ravin says.

Check out a sneak peek of de Ravin as Belle below:

Once Upon a Time airs Sundays at 8/7c on ABC.