There’s bigtime baby drama on Once Upon a Time this Sunday — and we’re not just talking about Rumple’s endeavor to reunite with his expectant wife.

In the episode “Our Decay” (Sunday, 8/7c), while Rumple attempts to transport Belle to the Underworld, Snow White and David will set out to send a message to their wee son, Neal, whom them left back home in Storybrooke before joining daughter Emma on her perilous journey.

After all, the Charmings planned to only be away for a short spell, in the name of finding and saving Hook. Instead, they and the other heroes have discovered a larger calling, to help in-limbo friends and frenemies settle their unfinished business. “Yeah, it’s not the best parenting choice,” Josh Dallas says of leaving Neal back in Storybrooke. “It’s not a great thing that they left him behind, and they’re feeling that.”

Dallas says that abandoning the tyke for an indeterminate amount of time understandably “drudges up” the Charmings’ experience with their firstborn, whom they transported to safety via an enchanted wardrobe, before the Evil Queen’s Dark Curse consumed the Enchanted Forest. “They don’t want to make a mistake like they did the first time with Emma,” says the actor. “So now that they’ve left Neal, they’ve got to try to get back to him” — or at least get a heartfelt message to their son, with the help of the Blind Witch (guest star Emma Caulfield) and an ersatz “phone booth.”

Yet despite their best intentions, the longer David and Snow (played by Ginnifer Goodwin) linger in the Underworld, the less certain a Storybrooke homecoming becomes. Especially now that there is an Underbrooke headstone with Snow’s name on it, and Emma’s plan to split her heart with Killian has hit a nasty snag.

Wanting to successfully rescue Hook but also get back home ASAP, “They’re being pulled in many, many directions,” Dallas says. Leaving Neal back in Storybrooke “might bite them in the ass.”

As Once co-creator Adam Horowitz previously forewarned of the Charmings’ crisis of conscience, “There certainly are consequences to that sort of headstrong jump into the Underworld, where they left a child behind. There are some really emotional things they’re going to have to deal with because of that.”

The emotional stakes are high for Emma as well, seeing as her heart-rules-the-head mission is what has put her folks in this dilemma in the first place.

“Her family decided to go with her, which means a lot to her and is incredible because she’s never had that support in her life before. But it’s also a lot of pressure,” Jennifer Morrison observes. “She feels very concerned that maybe they made the wrong decision by coming down there — and she would feel even more guilty if something bad happened to them. She has put a lot of pressure on herself to make sure that everyone is OK.”

Elsewhere in Sunday’s episode: Zelena and Regina get into a sibling squabble and Belle learns some shocking news that will change her life forever, while in flashbacks Hades pays Zelena a visit in Oz with the intention of striking an alliance, only to find himself with more than a partner in crime.

Want more scoop on Once, or for any other show? Email insideline@tvline.com and your question may be answered via Matt’s Inside Line.