"Once Upon a Time" fans could probably see a major character change for lead cast members when the show returns on ABC with season 5 on Sunday, 27 September, at 8pm.

Apart from Emma Swan (Jennifer Morrison), viewers can also except to watch the dark side of Snow White aka Mary Margaret Blanchard (Ginnifer Goodwin) in the upcoming sequel.

In the 30-second-long trailer, the followers of the fairytale drama can hear the voice of Goodwin's character saying, "Remember who you are Emma Swan. Resist temptation. I will not lose my daughter to darkness."

So it can be assumed that she will try her best to bring back Morrison's character from darkness. But until then, Evil Queen Regina Mills will be the new savior of Storybrooke.

"I think Regina's going to become the saviour and the hero this year. We don't know what's going to happen, and Regina is very experienced when it comes to sort of crossing over into the dark side and committing evil acts," said actress Lana Parrilla during an interview with Buddy TV.

The celeb also revealed that her character is worried about Emma Swan's future as she believes that "the saviour may never return back to her true self".

Meanwhile, "Once Upon a Time" fans who are eagerly waiting to meet Merlin aka Sorcerer will not see him in the premiere episode as executive producers Adam Horowitz and Edward Kitsis revealed that the character will appear in a latter sequel, according to Entertainment Weekly.