Things are about to get very complicated for Hook (Colin O'Donoghue) in season 5 of ABC's Once Upon a Time.

'Once Upon a Time's Snow & Charming 'Not Dealing Well' With Emma's Darkness

O'Donoghue spoke with Zap2it recently about his girlfriend Emma (Jennifer Morrison) succumbing to the dark side in the season 4 finale. Considering Hook's past, it's a supremely complicated situation.

"Hook spent hundreds of years trying to kill the Dark One and now his girlfriend is the Dark One so it's going to be complicated," O'Donoghue said (in the video featured below). "Hook loves Emma and he'll do whatever it takes to protect her heart and bring her back to being good again and being the woman that he fell in love with."

Emma Is 'Almost Sociopathic' When 'Once Upon a Time' Returns

O'Donoghue compared the same love Belle (Emilie de Ravin) felt towards Rumple (Robert Carlyle) to what Hook feels towards Emma.

"As much as Belle could see the good in Rumple, Hook is the same with Emma," O'Donoghue said. "Whether or not he decides to go dark again to try to get that back - I don't know. We haven't explored that yet, but it'll be interesting to see."

While Hook may venture back to the dark side for a little while, it is only for the good of protecting and saving Emma.

"Even in the last season when he was trying to be good he still had that little bit of darkness," O'Donoghue noted. "He's a pirate so he'll do whatever he has to do to protect the people that he loves."

Season 5 will pick up right where season 4 left off, with Emma disappearing into the darkness and leaving behind the Dark One's dagger, which had her name emblazoned on it.

Once Upon a Time season 5 premieres Sunday, Sept. 27 at 8 p.m. ET/PT on ABC.

Tags: Once Upon A Time television ABC