Mr. Gold (Robert Carlyle) will blackmail Regina (Lana Parrilla) in the next action-packed episode of ABC's Once Upon a Time.

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ABC has released a new plot synopsis for the next episode of Once Upon a Time, which is titled Heart of Gold. As suggested by the title, this will be a big episode for Gold as he becomes even more hellbent on finding his happy ending.

However, Emma (Jennifer Morrison) may be our only hope.

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"Emma is still reeling after learning the truth of her parents' history with Maleficent [Kristin Bauer van Straten], but she must focus on finding the Author, who is running loose in Storybrooke, before Gold does," the synopsis reads. "When Gold's quest for his happy ending grows more urgent, he blackmails Regina into helping him."

Meanwhile, the episode will feature a Fairy Tale Land flashback in which Mr. Gold/Rumplestiltskin asks Robin Hood (Sean Maguire) to steal a "valuable magic elixir" from the Wicked Witch (Rebecca Mader).

That's right, the Wicked Witch is back but of course only through flashbacks. The Wicked Witch/Zelena's return was heavily previewed in the promo for this episode, to the point that it was the entire focus of the promo.

Fans will remember that Zelena was actually killed by Rumplestiltskin during the second half of season 3, back when she was the main villain.

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