'Once Upon a Time' stars dissect the heartbreaking winter finale 

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VANCOUVER, Canada — Have you caught your breath yet from Sunday\'s

Yeah, it was a tough one. In the episode, title "Swan Song," Emma (Jennifer Morrison) was prepared to sacrifice herself to get rid of the darkness forever, but before she could, the love of her life, Hook (Colin O\'Donoghue), got hold of Excalibur and sacrificed himself instead. He has now been sent to the underworld.

See also: All the big moments from the \'Once Upon a Time\' winter finale

The ever-crafty Gold (Robert Carlyle) took all the darkness and, when the next half of the season picks up in March, he’ll be more evil than ever, as Emma and her family/friends try to bring Hook back.

While we have some time to wait until March, Morrison and O\'Donoghue were more than happy to chat about the shocking developments when

First up, Morrison took a break from filming to answer questions about Emma’s motivations and losing her loved one after everything she did to try to save him.

MASHABLE: Why do you think Emma decides the best thing to do is to sacrifice herself?

Jennifer Morrison: I think ultimately Emma knows she\'s responsible for the circumstances, and it’s deeply upsetting and conflicting for her to come to that conclusion — not because she doesn\'t want to save everyone but because she has evolved. She has grown so much in this journey, and she has gotten to a place where she is at peace with herself. And some of that strength comes from the peace within herself, and she knows she has to take responsibility for her decision, and she wants to do what it takes to save the people that she cares about. She doesn’t see another choice.

What\'s the state of Emma\'s magic beyond this episode?

She’s back to savior magic. Her savior magic is intact. There is a mention that in the initial arrival in the underworld, anyone who\'s dealing with magic is shaken a little bit, but Emma sinks into hers pretty quick. So she’s back into true savior Emma form in terms of magic pretty quickly.

In regards to Hook and Regina’s backstory, how much of that does Emma know?

I think that there\'s going to be parts of this that she knows because they are teamed up. We operate from the assumption that certain things get shared off screen and there are certain pieces of information that each character is sharing with each character even if the audience doesn’t see it ... she probably knows the CliffsNotes version of it, but she doesn’t know the actual details.

What does Emma think of Hook’s ultimate sacrifice?

I think that she\'s aware of what it\'s like to have the darkness inside of you now that she\'s been the Dark One, and she knows how the darkness works. She knows its manipulations and its power. Her ego is not involved when it comes to Hook\'s choices once the darkness is within him. She\'s very aware of what is taking hold of him and why it\'s happening.

But in terms of him deciding to make the sacrifice, she\'s devastated because she feels responsible and feels like it should be her. She\'s done so much to keep him alive and now she\'s going to lose him anyway. But she knows she can\'t deny him this because that’s exactly what he was saying to her in the first place, which was, \'You should have let me die when I was cut by Excalibur in the first place\' and she couldn’t. She selfishly hung onto him. She did that because she wanted to keep him with her and now she knows that that choice isn’t going to save him or anyone and unfortunately she has to give in to it.

Is it safe to say everyone is pointing a finger in some way at Gold?

Gold is definitely held responsible for taking away the act of heroism that Killian offered, so that is where the betrayal feels strongest because he really did have to overcome so much. Clearly the darkness had so much over him and the true man that he is had to overcome so much in order to do so much in that moment and do the \'right thing,\' which was to sacrifice himself.

Ultimately, he thought he was sacrificing himself for a much greater good, which was that he was going to destroy all darkness forever, not just be the Dark One. He thought he was doing this for a much greater good and making an eternal sacrifice in a sense. That was all taken away so that is the root at betrayal that everyone is pointing at Gold for.

In the below interview, O’Donoghue gives his take on Hook’s sacrifice and what we learned in the flashback about his past secret with the Evil Queen.

MASHABLE: Let’s talk about the sacrifice. Is it his love for Emma that pushed him to do that or is there more to it?

Colin O’Donoghue: Ultimately, it\'s his love for Emma that causes him to break through the darkness and realize what he\'s done, and he\'s willing then to sacrifice his life and condemn himself to hell in order to save her, which is a pretty big thing to do. I think people — certainly the fans of Hook and Emma — will get to see that deep down inside he really does love her and the power of that love is what breaks through and helps him realize that the dark path he is on is not right. [That\'s when] he\'s willing to go to the underworld.

It\'s a pretty emotional moment for both of them, Emma and Hook, because she asks him to sacrifice him and kill him and she, naturally, doesn\'t really want to do it even though she says she’d do whatever it takes to protect her family. But essentially he’s the man she loves and she’s the woman he loves.

I was just as blown away by the flashback portion where Hook kills his father as well as Regina’s part in that.

I think that that gives it a little bit of flavor of the type of nefarious darkness that Hook gave in to when he was younger [and] why or how the darkness was able to take such a hold of him. His father betrayed him, and Hook sees that and sees that his father is about to do that with his new son. In that moment, there is so much anger and hatred and he sees himself in that little boy and he sacrifices his father.

Regina, essentially, is the architect of that, and that\'s what their secret was — that she is part and parcel. It was interesting for me to see his relationship with his father. You see how sad a character the old Hook was until he met Emma and realized he could try to forgive himself because someone was willing to love him.

Would you say that killing his father is what changed Hook in the past?

He changed before that to become Captain Hook, but killing your father is a pretty big thing. [

] Essentially, he was willing to help his father. Regina put him up to killing him, and Hook was about to do it but then his father gives him a bit of a spiel and [Hook] thinks that he’s ready to redeem himself. Hook then is willing to save his life until he sees him with the little boy and sees he\'s about to do the exact same thing to him. I think that’s when Hook gave into his previous darkness.

Do we think that Hook is like his father despite everything his father did?

It’s interesting because at times Hook portrays himself as being similar and doesn’t care about the world, but I think deep down Hook has always had a code. I don\'t think he\'d abandon his son or his sons consistently [like his father did]. I think deep down he wouldn\'t do that. He wouldn\'t abandon them, and I think in that respect he is different.

You\'ve seen him on the ship with Baelfire, and Hook was willing to genuinely give up being a pirate and try to be a father to this boy and essentially he betrays him. But I think if Baelfire had said, "Yes, I\'ll stay here with you," he would\'ve given it all up. But then he does the most heinous thing when Baelfire says, "No, I don’t want to do that." Hook betrays him completely. On one hand, you see a slight gentleman and then the other hand you see this tyrant.

How has it been working with Jennifer in the first half of the season since you were both playing different shades we hadn’t seen before?

Look, Jen is absolutely brilliant all the time and we have a great working relationship on set and we enjoyed doing our scenes together. It\'s been fun playing two completely different characters trying to relate to each in the way that old Hook and Emma related to each other, but they just keep missing the mark because they’re Dark Ones so it’s been interesting to see that. Getting to play Dark Hook was really a lot of fun. And I genuinely think that this season is one of the best seasons, if not the best. Writing wise, I think it\'s dark and it\'s just really, really good. It’s been a great season.

will return for the second half of season five in March 2016.

These interviews have been edited for grammar and slightly condensed.