Emma (Jennifer Morrison) and Rumple (Robert Carlyle) will go to the Underworld to save Hook (Colin O'Donoghue) in the upcoming winter premiere of the ABC series "Once Upon a Time."

In the finale, Hook had a change of heart about his plans to send everyone to Hell. He asked Emma to kill him after channeling all the Darkness inside her and all the other Dark Ones he summoned. Hook heeded Regina's (Lana Parrilla) words that he could not murder his family. At the last minute when Nimue was about to finish Emma, he decided to save the latter. Hook wanted to die a hero, and although Emma was heartbroken, she agreed with his request that he dies in her hands.

When Hook and all the Dark Ones got sent to the Underworld, Emma told Rumple that she could still hear the dagger whispering to her. It was supposed to be gone when the Excalibur turned to ash. Rumple then admitted that the dagger he gave her was not the real one, as it was only enchanted to kill all the Dark Ones, including Emma's lover. Rumple wanted to be the only Dark One left, and to do that, he tricked all of them.

Emma was furious, but she realized that she has the upper hand at the moment. She told Rumple that Belle (Emilie de Ravin) would know about his trickery and see how she would react to it. Belle has just returned to Rumple after learning of his "selflessness." If she would discover that he was not the hero he was portraying himself to be, Belle would once again hate him. Rumple had no choice but to follow Emma's demands, which was to go to the Underworld with her and save Hook. Will they succeed?

Meanwhile, Entertainment Weekly reports that episode 12 titled "Souls of the Departed" will feature a big family reunion. Regina's father Prince Henry (Tony Perez) will reportedly return and join the other Dark Ones from the Underworld. Some other characters who will reappear for the special episode include Peter Pan (Robbie Kay), Cora (Barbara Hershey), Sidney Glass (Giancarlo Esposito), and the Blind Witch (Emma Caulfield).

Showrunners Adam Horowitz and Edward Kitsis recently spoke to Variety on how excited they were for the winter premiere, which also happens to mark an important milestone for the ABC series.

"The hundredth episode for us — and the second half of the season — what we're really excited about is, we feel like we're going to be honoring the show by really giving you that season one feeling all over again," Kitsis said.

"Once Upon a Time" season 5 will return on March 6 at 8 p.m. EST on ABC.