On the upcoming fourth season of ABC's Once Upon a Time, Henry (Jared Gilmore) will be trying his hardest to get Regina (Lana Parrilla) to stay on the side of good.

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Once Upon a Time co-creator Edward Kitsis spoke with Entertainment Weekly recently about Regina and her potential for going to the dark side again after Emma (Jennifer Morrison) brought Robin Hood's (Sean Maguire) Maid Marian (Christie Laing) back from the past.

Henry will try to prevent Regina from going full-evil in Season 4.

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"We're going to see Henry on a mission with Regina this year," Kitsis explained. "And maybe some of his light side will rub off on her."

Meanwhile, fellow series co-creator Adam Horowitz revealed to TVLine that they would be delving into Captain Hook (Colin O'Donoghue) and his backstory again.

"There is more delving into his past to come," he teased, though the mystery behind whom Hook traded his Jolly Roger with in exchange for Emma will be revealed "somewhere down the road."

In the midst of everything will be the introduction of Frozen. Various characters from the blockbuster animated film will be featured in Season 4, including Elsa (Georgina Haig), Anna (Elizabeth Lail), Kristoff (Scott Michael Foster), Hans (Tyler Jacob Moore) and Pabbie, the elder troll (voiced by John Rhys-Davies).

Once Upon a Time Season 4 is set to premiere Sunday, Sept. 28 at 8 p.m. ET/PT on ABC.

Watch a preview for the new season here:

Tags: Once Upon A Time television ABC