Co-creators Adam Horowitz and Eddy Kitsis talk to THR about Emma’s mission to find Hook, the rules of the underworld and characters making a comeback in the second half.

[Warning: this story contains spoilers from Once Upon a Time’s season five winter finale, "Swan Song."]

Hell hath no fury like a Savior scorned. In Once Upon a Time’s winter finale, Emma (Jennifer Morrison) was forced to kill her love, Hook (Colin O’Donoghue), to save Storybrooke from the underworld, but in a huge twist, she ended up going down there anyway.

Once she discovered that Rumplestiltskin (Robert Carlyle) channeled all of the Dark Ones’ magic into himself, she demanded that he take her down to the underworld to save Hook, and in the final moments of the finale, the whole gang — including Mary Margaret (Ginnifer Goodwin), David (Josh Dallas), Regina (Lana Parrilla), Robin Hood (Sean Maguire), and Rumple — headed on a rescue mission.

THR spoke with co-creators Adam Horowitz and Eddy Kitsis to discuss the second half of the season, and they revealed details about Emma’s quest for Hook, the familiar face ruling the underworld, and if characters like Zelena will be returning next year. Plus, the bosses also break their silence on whether star Emilie de Ravin’s pregnancy may be written into the show now that Rumple and Belle have rekindled their love.

The underworld looks just like Storybrooke. Is this something that changes for whoever goes into it, or is that just what the realm looks like?

Adam Horowitz: What the underworld is and why it looks the way it does is a part of our storytelling coming up. So while we don’t want to spoil it, we can say that there is a very specific reason why it looks like Storybrooke, and it has to do with some of the folks we’re gonna meet down there.

Are only evil people in the underworld? It’s like hell, right?

Horowitz: It’s not hell. The underworld isn’t hell — it is a place between. It’s the place for people with unfinished business, so it’s not about good or evil.

Eddy Kitsis: The second half is a lot about them getting closure on their pasts and how the past comes to haunt you.

There are also going to be some new characters in the second half of the season: Hercules, Meg and maybe Hades. Will that be separate from the underworld or intertwined?

Kitsis: That is kind of in it. We’re going to meet some new people in the underworld, but I think a lot of what people are going to see — kind of in honor of the 100th episode in our fifth year — is really seeing a lot of people from our past who we haven’t seen in awhile.

For Emma’s journey, is the biggest battle trying to find Hook in the underworld or fighting against the people from everyone’s pasts to get to him?

Horowitz: It’s going to be a bunch of things. It’s not just about finding Hook, it’s about what happens when Emma and all of our characters enter this realm and have to face things both from their past and present. It will hopefully be an exploration of our characters and how they react to facing things you never thought you were going to face.

If someone is stabbed in the underworld, are they dead forever? Is that something they can come back from?

Horowitz: That’s actually a great question, and the rules of the underworld — what it means to be there, whether you can leave, how you can leave, where you go ...

Kitsis: ... Are going to be explained by our favorite, favorite tour guide of the underworld, and her name is Cora.

Is Cora the mayor of the underworld? She was sitting in Regina’s chair, so is it safe to assume there?

Kitsis: That is safe to assume. She definitely has the place — well, she understands the place, yeah.

Is Hook the same guy that Emma fell in love with now that the darkness was purged from him? Now that he’s in the underworld, has he changed at all?

Horowitz: I would say he’s gone through a lot, as has Emma, as have all of them, so no one’s the same. But if you’re asking if he’s still dark, then no — that was handled in the finale.

Kitsis: Yes, all of the darkness was given to Gold.

Did Rumple make this plan thinking that Belle would be gone forever and it was OK for him to be dark now that she was exploring the world? Or did he know his plan would work and think maybe she would come back?

Kitsis: I think when he said goodbye to her, he really did it so she wouldn’t have to see what happens to him and everyone else. He wanted her to be safe from the darkness. It was a very genuine moment. And then what happened was a crime of opportunity where he saw a way to no longer have to die and go to the underworld, and I think in a lot of ways, what Hook was saying in the opening was that he loves that dagger and it’s a part of him.

It’s clear that Rumple and Belle rekindled their relationship. Are you considering writing in Emilie de Ravin’s pregnancy now?

Kitsis: I would say it certainly looked like they re-consummated their marriage, so we’ll just have to wait and see, but I would say you’re definitely on the right clue trail.

What kind of powers does Rumple have versus his old ones? Are they just magnified by all of the Dark Ones, or is it a new kind of magic?

Kitsis: I think he definitely has all of the powers of those Dark Ones and he’s emerged stronger and probably even a little wiser. Very dangerous.

Have we seen the last of Zelena?

Horowitz: No, we have not seen the last of Zelena.

Kitsis: Absolutely not! You can’t keep a good witch down, and that has been the theme of this show since the beginning.

Is that something that will be explored post-underworld, or will that be intertwined?

Kitsis: It will be soon, and we will see her return. Maybe not after the first couple episodes next year, but we’re going to see her in the middle and then she’ll be a large part of the second arc.

With Regina and Robin and Zelena’s baby, if they do get back to Storybrooke, will they co-parent the child?

Kitsis: It’s tough, because every time they lead Zelena in, she certainly seems to not want to play ball. Last week’s episode, they were ready to share custody so she could see her [daughter], and when she thought they were going to die, she turned on them. I think there’s a lot of family dynamic to work out there.

Are Regina and Robin ready to just raise that baby now that Zelena’s gone?

Horowitz: I think there are some really pressing issues that are complicating all of the family dynamics, and part of the second half of the season will be untangling all of that.

What about Arthur? Is he gone, or will we see him come back?

Kitsis: There’s potential. We know there’s still Arthur and Merida and Guinevere in Storybrooke, so we may see them a little bit at the end of the year, but not for a while.

Will Mulan and Ruby come back to Storybrooke if the gang makes it back?

Kitsis: Yeah, we are going to see Mulan and Ruby. We will see them in the second half of the season.

Will we see Hook’s half brother come into play? He was briefly mentioned when Hook killed his father in flashbacks.

Horowitz: You mean Liam 2? (Laughs.)

Kitsis: I can tell you we will definitely see Liam 1, but whether we see Liam 2 is up in the air.

Is everyone on board with Emma’s plan as a team effort, or is she going to go on a solo mission to save Hook?

Kitsis: I think it’s a team effort. Everyone is going with the anticipation of that Emma has a plan, we’re all going to go together, we’re gonna go in there, grab Hook, split the heart, and get out.

It won’t be that easy, though.

Kitsis: It never is! But the best intentions. The road to hell is paved with the best intentions.

You put Emma through a lot. Every love interest she’s had has died. Do you see true love in Emma’s future, whether it’s with Hook, or if she’ll have to move on and find someone new who doesn’t die?

Kitsis: I’ll tell you what — I think that is going to have to be a question she has to solve. The reason she is going down there is for that very reason. She finally lowered that wall and let Hook in, so she doesn’t want to lose another person who she loves. So echoing her father’s line, "I will always find you," and I think come hell or high water, she’s gonna try.

Once Upon a Time returns Sunday, March 6 at 8 p.m. on ABC.