'Once Upon A Time' Star Rebecca Mader Teases 'Mind-Blowing' Episode

Tonight's episode of Once Upon a Time is entitled "Sisters" and, as might be guessed by that title, the episode will finally give fans an inside look at what has developed between Regina (Lana Parrilla), Zelena (Rebecca Mader), and Cora (Barbara Hershey). The episode will tell the story of these three women in flashbacks, and Mader promises it will be an episode not to be missed.

Once Upon A Time Delves Deep Into The Past For "Sisters"

Rebecca Mader says tonight's episode is not to be missed by Once Upon a Time fans eager to learn more about the relationship between Regina and Zelena, because this episode will reveal much about their past relationship and how they arrived at the people they are in the present. The Once Upon a Time actress says the relationship between her character and Regina is her favorite story arc, because there's so much to learn. She adds that, even in the present, the relationship between these two characters is still evolving.

"It's really, really, really good," says Once Upon a Time's Mader. "When I read the episode, I was just really moved and really blown away. It's interesting to find out. … I really can't say too much. Regina is ultimately trying to stop Zelena and Hades getting together. The fans are going to lose their minds."

Rebecca says the episode will reveal a deeply buried family secret and that the secret will really rattle Once Upon a Time fans. Mader says the episode really becomes wild at that moment and even she lost her wits, when she previewed the Once Upon a Time episode.

"I literally fell off my sofa, so when you do find out, you'll probably fall off yours. You should probably wear a seatbelt. It's pretty mind-blowing," added Rebecca.

Many Once Upon a Time fans may be rolling their eyes, recalling some pretty epic reveals and twists from past story arcs, but Mader insists there's little else like this reveal. She says it's one of the biggest in the entire history of the ABC series.

Rebecca Mader Says Hades Melts Zelena's Heart

Elsewhere in tonight's Once Upon a Time episode, Mader reveals that the love between Hades (Greg Germann) and Zelena continues to flourish, but growing feelings for her sister may prevent Zelena from the final follow through. It's a struggle, because Hades has confessed his love for her and Mader says her character does want to trust him. Hades seemed to be baring his soul to Zelena, telling her of his plan to escape the Underworld, after true love's kiss restarts his heart.

Adding tension to Zelena's struggle on Once Upon a Time is the realization that Storybrooke's heroes are after Hades, but they aren't pursuing her. She has a chance to change her fate and that's appealing to her as well, because she does want family and love.

"Their vengeance is towards Hades, they hate him but they don't hate me. And I want to be with him, but that means the expense of them…. Her morals are starting to kick in, her values are changing, her heart is opening…. Having a kid is softening her, so it's a really complex, interesting time in her arc," says the Once Upon a Time actress. "And it's been really, really fun to play, I've really enjoyed it."

Mader says her character has really changed, since her first appearance on Once Upon a Time, and one of the biggest things to have changed Zelena is having her daughter in her life. She's less concerned with getting revenge on Dorothy and indulging her wicked ways, because she has her daughter to care for. Between Regina and her own daughter, Zelena is beginning to feel connected to something greater and that causes an internal struggle, due to her feelings for Hades.

Once Upon a Time airs tonight on ABC.

[Image by ABC]