Here is the promo for the 18th installment of Once Upon a Time season 6. The episode is titled “Where Bluebirds Fly”.
In flashback, Zelena befriends a young woodcutter who has been cursed and turns to her for help finding a new heart. Zelena is forced to choose between keeping her powers and her friendship with him. Meanwhile, in Storybrooke, Zelena decides to take on the Black Fairy and put a stop to her, once and for all, against Regina’s wishes, and the Charmings disagree over Emma and Hook’s wedding plans.
Once Upon a Time Season 6 Episode 18 airs on April 23 at 8|7c on ABC.