As one would assume, there will be many big moments in the winter finale of ABC's Once Upon a Time, but one involves Robin Hood (Sean Maguire) picking either Marian (Christie Laing) or Regina (Lana Parrilla) as his mate.

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Parrilla spoke with TVGuide.com about what was ahead for the winter finale, titled Heroes and Villains, including who Robin Hood chooses and what will become of Operation Mongoose.

"Robin Hood has a difficult choice to make," Parrilla said. "He has to choose between these two women. Having a son with one and a history with her, and this newfound love with Regina is a very difficult decision for him. You'll see who ends up choosing this Sunday and what happens."

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The three have been in a unique love triangle, considering Marian has been frozen for most of the fourth season.

As for Operation Mongoose, Parrilla suggested that it would be picked up again going forward, after being mostly sidelined for the first part of season 4.

The Author is a very important character, this person or thing or whatever it is, is responsible for everyone's fate," Parrilla noted. "This for Regina has become her No. 1 priority. She is so focused on figuring out who this author is because once she gets ahold of this author, then everything can fall into place for her. Or at least that's how she is hoping it will turn out."

She also discussed how working with Henry (Jared Gilmore) in this mission has benefited both of them, particularly with Henry having the heart of the truest believer and being a consistently positive force for her.

"There will be clues that will be revealed in the second part of the season that will help us find who the author is," Parrilla teased.

Once Upon a Time airs Sundays at 8 p.m. ET/PT on ABC.

Watch the promo for the next episode of Once Upon a Time here:

Tags: Once Upon A Time television ABC