Mr. Gold/Rumple (Robert Carlyle) and Belle (Emilie de Ravin) are in for a bumpy ride in the coming episode of ABC's Once Upon a Time.

From the get-go, Mr. Gold and Belle have had a complicated relationship, and this won't change during the second half of the season. Belle realizes what Mr. Gold did by giving her the potion to help her leave town instead of keeping it for himself, for which Belle is immensely grateful.

Now, Mr. Gold is heading to the Underworld to help out in the quest to retrieve Hook (Colin O'Donoghue), but Belle is still unaware that Gold has become the Dark One again.

Carlyle spoke with Entertainment Weekly recently about the status of Belle and Gold's relationship, suggesting that it will be complicated.

"When she came back, she realized that Gold, for the first time, had been completely unselfish and sacrificed himself for her," he said. "He could've used that potion and could've gotten out of town himself, but he hasn't. He's given it to her. But unfortunately just at the point she's come back, she's come back to the Dark One. How she's going to react when she finds that out again, that Rumple-Belle relationship is thrown into chaos and influx."

Once Upon a Time co-creator Adam Horowitz previously spoke with TVLine about what their plan is for Belle in the second half of the season. Even if she's been put on the back burner for now, her storyline will ramp up in the weeks to come.

"We have plans to keep Belle busy. Although she didn't get on the boat [to the Underworld] with our heroes, she's important to the story and becomes very involved," Horowitz said.

Even though Rumple has become even darker than before, "We left [Belle and Rumple] in a place where that relationship was evolving . . . We're not abandoning any of those story threads, and we're hoping to pick up on them in an unexpected way."

Once Upon a Time airs Sundays at 8 p.m. ET/PT on ABC.

Watch a promo for the next episode of Once Upon a Time here:

Tags: Once Upon A Time television ABC