'Once Upon a Time' Season 5 spoilers: Peter Pan, Regina's mother and Underworld mission to find Captain Hook in episode 12 [WATCH]

Emma Swan (Jennifer Morrison) has vowed in the winter finale episode of “Once Upon a Time” Season 5 that she will find Captain Hook (Colin O’Donoghue) after losing him to Rumplestiltskin’s treachery. The preview video of “Once Upon a Time” Season 5, episode 12 titled “Souls of the Departed” teases that Emma, along with her family and friends, will be on a quest to bring back Captain Hook from the Underworld where they will come across old and new characters.

Spoiler Alert: This feature contains major “Once Upon a Time” Season 5 spoilers.

Some of the old “Once Upon a Time” (OUAT) characters that will appear in episode 12 of ABC’s fantasy drama series are Peter Pan (Robbie Kay) and Regina Mills’ mother, Cora (Barbara Hershey). Additionally, the Storybrooke heroes are surprised to see that their town has become the Underworld.

In an interview with The Hollywood Reporter (THR), OUAT series creator Adam Horowitz and Edward Kitsis explained that there is a specific reason why the Underworld looks like Storybrooke. “It has to do with some of the folks we’re gonna meet down there,” Horowitz teased.

Horowitz further added that the Underworld is not hell but a place for those who have unfinished business. Kitsis has revealed that the second half episodes of “Once Upon a Time” Season 5 will be about those characters getting closure on their past life.

When it comes to the rules of the Underworld, Kitsis teased that the OUAT character who understands the place is none other than Regina’s mom, Cora. Horowitz and Kitsis further teased that Cora will be the one to explain to the Storybrooke heroes the rules of the Underworld like if they can leave the place, how can they leave and where they will go.

The other storylines to look forward to when “Once Upon a Time” Season 5 returns from its winter hiatus include Mr. Gold/Rumplestiltskin (Robert Carlyle) as the Dark One again, Mr. Gold’s relationship with Belle (Emilie de Ravine), Captain Hook’s brother Liam and the return of characters Mulan (Jamie Chung), Ruby (Meghan Ory), King Arthur (Liam Garrigan) and Zelena/Wicked Witch of the West (Rebecca Mader).

Horowitz and Kitsis confirmed that Zelena will still come back even though her half-sister Regina Mills/Evil Queen (Lana Parrilla) transported her back to Oz in the winter finale episode of “Once Upon a Time” Season 5. “We’re going to see her in the middle and then she’ll be a large part of the second arc,” Kitsis teased.

With Zelena’s return, the storyline on Regina and Robin Hood (Sean Maguire) and Zelena’s baby will also be explored in the second-half episodes. “Once Upon a Time” Season 5 is scheduled to return with episode 12 titled “Souls of the Departed” on March 6, 2016 at 8/7c on ABC.

Watch the “Once Upon a Time 5x12 Promo ‘Souls of the Departed’ (HD)” video: