Colin O’Donoghue talks to THR about whether Emma and Hook's relationship can survive his evil plan and what to expect from flashbacks with the pirate’s father in the ABC fantasy series' winter finale.

Once Upon a Time is about to enter the depths of hell, and Captain Hook (Colin O’Donoghue) is leading the evil charge.

In the fairytale drama’s season five winter finale, Dark Hook’s plan will take the pirate down his darkest path yet as he snuffs out all of the light in Storybrooke with original Dark One, Nimue (Caroline Ford), by opening up a portal to the underworld. And if he has to take down his ex-girlfriend Emma (Jennifer Morrison) and her family to get the job done, he’s willing to make that sacrifice.

When The Hollywood Reporter caught up with O’Donoghue, he revealed that Hook has completely given himself over to the darkness in order to get revenge on Rumplestiltskin (Robert Carlyle), and he’s too drunk on power to stop for anyone. But does that mean he is willing to kill his former love to enact his plan? Find out below, plus how the show will dive into Hook’s past with his father and the Evil Queen.

What will happen when Hook’s dark plan unravels? Is his revenge plot still about killing Gold, or has it shifted to be about Emma now and all of the light in Storybrooke?

Well, that’s presuming that his plan unravels. His thing is revenge on Rumple, and he’s willing to let the darkness use him in whatever way it needs to get that done. Transporting everyone into the underworld through that portal is his way of getting revenge on Rumple.

Hook threatens everyone that Emma loves in the preview, and it looks like he grabs Henry. Is there anyone whom we should be most afraid for?

He’s enveloped with the darkness and is willing to do whatever it takes to make his plan a reality. Still, deep down there’s an element that they can still love that we see with Rumple still loving Belle and Emma loving Hook. But I think at this stage, he’s so angry with her and hurt because she did the one thing that he begged her not to do, because he knew he couldn’t fight against the darkness. He knew he didn’t have the willpower to do that. So he’s more of a pissed off boyfriend than wanting Emma to die in any kind of way. But at this stage, he’s just so angry, and when the Dark One gets angry, you do insane things.

Hook and Emma both threaten to kill each other. Do they genuinely want to do that, and will he kill Emma if she’s the only thing in his way?

When you are the Dark One, it’s very difficult to even think. You saw with Rumple’s betrayal of Baelfire, the only person he really cared about, and I think at that point, you’re not afraid to betray the people that you care about, even if it hurts you. You are sort of drunk on the power of darkness. I don’t know if necessarily killing Emma or Emma killing Hook is a thing that they would or wouldn’t do, but whatever it takes on both sides, they’re willing to do.

Is there any hope for Emma and Hook? Is the only way they could be together if the darkness is gone from them both?

That’s an interesting question. The darkness is one of those things where I think if they’re both dark, I don’t know if that could work. At the minute with the way that Hook is, it’s a very difficult thing to see happening … it’s complicated. (Laughs.) Much like most of their relationship, to be honest. It’s pretty much a complicated thing.

Are we meeting Hook’s father in flashbacks in this episode?

We still see elements of Hook’s father and what his relationship with him was and a bit more of Hook’s backstory as well in fairytale land.

Does Hook’s father influence him in an evil or bad way? We know he abandoned him as a kid and there’s some sort of adventure with the Evil Queen involved.

We’ll see Hook’s prior relationship with the Evil Queen and an element of that, and we will see Hook’s father in those flashbacks at some point.

Lastly, why does Hook trust Nimue? She’s this ultimate Dark One and she could easily betray him and take over his plan.

It’s not necessarily that he trusts Nimue, but the darkness is all of them, so she’s part of him now. All of their wholesome desires transfer over from one Dark One to the next person. This plan is one that all of the Dark Ones wanted to enact, and even deep down, Emma wanted it to happen. As she said, she knew what the plan was going to be — it’s something they can all feel because the darkness is an entity in itself that takes over a host’s body. So Nimue is essentially Hook, and she’s part of Emma. Hook is willing — well, actually, Hook essentially has no choice because he’s embraced the darkness. He will let it use him to get what he wants so long as he gets his revenge on Rumplestiltskin, which is what he wants. That’s kind of where that is. It’s not trusting or not trusting, because he really has no choice. It’s who he is now.

Once Upon a Time’s winter finale airs Sunday at 8 p.m. on ABC.