'Once Upon a Time' Star Colin O’Donoghue Previews the 'Fantastic' Season Finale

He teases Hook and Bae’s 'complicated' relationship in Neverland.

In last season’s finale, magic returned to Storybrooke.

This year, Storybrooke may be completely destroyed.

Sunday’s heart-stopping finale of "Once Upon a Time" has Greg and Tamara pulling the trigger to wipe out the town and all its fairy-tale denizens. Helping them is none other than the dastardly Captain Hook, whose sole focus is the death of Rumplestiltskin.

[Related: 'Once' Star Teases Wormhole Destination]

Fans will also learn more about Hook’s relationship with Rumple’s son, Bae, who he fished out of the ocean in Neverland last week. We chatted with star Colin O’Donoghue about Hook’s intentions, how far he’ll go for vengeance, and whether we’ll see Neverland again next season.

Last week, Hook brought Bae onto his ship. What can we expect from them this week?

This week, obviously you're going to see Hook's interaction with Bae in Neverland. Hook is intrigued by this boy that he's pulled up out of the sea; he obviously doesn't know who it is when he pulls [the boy] out. It'll be interesting for people to see the history that Hook and Bae have together.

What is their relationship like? How does Hook regard him?

If he finds out who Bae is, Hook is sort of caught in a little bit of a position there, because he was in love with Mila, Bae's mother, but has this deep hatred for Rumplestiltskin. It's a funny situation for him to be in. You're going to see him trying to figure out what to do with this boy and what he can get from having this boy on the ship. They've got a very complicated relationship.

[Related: 'Once Upon a Time': Will Regina Sacrifice Herself to Save the Residents of Storybrooke?]

We saw that Peter Pan -- if that’s who the shadow is -- isn’t quite a good guy. So does this mean Hook isn’t the bad guy of this story?

Hook, in the context of "Once Upon a Time," is quite complicated. Hook of old is described as this evil character, and I think what's great about the way that [creators] Eddie [Kitsis] and Adam [Horowitz] have created Hook is that he's a little bit more complicated than that. It's not that he's just outwardly evil -- he has the potential to be compassionate, he has the potential to be good. But he also has the potential to be quite nasty and cruel.

It seems like Neverland is a darker place than the one we’ve all read about.

Eddie and Adam are great at taking a well-known story that we all grew up with and making it kind of edgier or putting some sort of different slant on it. It's definitely not the Neverland that people will have seen before.

It seems like Hook helps Greg and Tamara release the trigger. But this is a guy all about self-preservation. He must have a backup plan, right?

Hook definitely always has a plan of some kind. Hook's kind of in it for himself, so whatever Greg and Tamara can do to help him achieve his aim, he'll go along with it. But there will be other times where he'll be just as happy to turn his back on them, or whoever he's working with at the time. You've seen that with Cora and with Regina.

Hook is bent on killing Rumplestiltskin. But there’s also a prophecy that Henry is his undoing. If Hook found out, would he stoop so low as to use Henry?

I haven't really thought about that... He might. He could potentially use Henry. He could potentially use anybody to reach his own aims. I haven't thought about that actually. Maybe it's one to pitch to Eddie and Adam. (Laughs)

Any interaction between Emma and Hook? Those two have always had sparks.

They're definitely attracted to each other. You see Hook interacting with a lot of people. They definitely have a connection, Emma and Hook. Whether it's any more than that, who knows?

Last season ended on a big cliffhanger. Will this season?

Yes. (Laughs) It's fantastic.

And can we expect to see more of Neverland next season?

I don't know much about what would happen next season. I would hope that we would see more, find out more about Neverland. Definitely it would be nice to see more of Hook's backstory and what he's about and how he's become the man that he is.

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The "Once Upon a Time" season finale airs Sunday, 5/12 at 8 PM on ABC.