“Once Upon a Time” fans are going to want to brace themselves, because episode 20 is gearing up to be an emotional rollercoaster. Titled “Mother,” the episode will find Emma (Jennifer Morrison) and Regina (Lana Parrilla) returning to Storybrooke with Lily (Agnes Bruckner) … but not under the best circumstances.

For those that missed episode 19 last Sunday, the ABC series introduced viewers to adult Lily, Emma’s friend from her foster home days. Emma had just discovered that Lily was actually Maleficent’s (Kristin Bauer van Straten) daughter. But that news was something that Lily put together a long time ago thanks to a visit from the Sorcerer’s Apprentice. Unfortunately for Emma, this didn’t make the situation any easier. In fact, it complicated things because Lily revealed that she wanted revenge on Emma’s parents, Mary Margaret (Ginnifer Goodwin) and David (Josh Dallas).

Already on the edge of darkness, Emma nearly killed her old friend when she discovered what she had up her sleeves. Thanks to Regina, she was able to take a step back and cool down. However, Regina was also thrown a curveball in episode 19. After bringing Lily along for a pit stop to New York City to warn Robin Hood (Sean Maguire) about Zelena (Rebecca Mader) impersonating his wife Marian (Christie Laing), Zelena dropped a bombshell on everyone – she’s pregnant with his baby.

So, where does that leave our favorite fairytale characters in episode 20? In a big ol’ mess!

Emma will follow through on her word to Maleficent and bring Lily back to Storybrooke to reunite the mother and daughter. But the promo video for “Mother” previews that Emma could be making a big mistake.

“So, how are we going to get revenge on Snow White and Prince Charming?” Lily asks Maleficent.

Meanwhile, the synopsis teases that Regina has bigger fish to fry. Robin and the former evil queen will “struggle with the implications of Zelena’s pregnancy.” However, a happy ending may still be within her reach. Regina will turn to the Author (Patrick Fischler) for answers about the fairytale book drawing of her and Robin Hood from the Enchanted Forest of the past. It’s unclear if he’ll be able to give her answers, but “Once Upon a Time” fans will definitely get to see Regina’s mother again thanks to a flashback to the anniversary of Daniel’s murder.

Finally, things will not be looking good for Gold (Robert Carlyle). His health will continue to decline, forcing the Author to look to for a “new ally” in order to get his hands on the magic ink.

“Once Upon a Time” Season 4, episode 20 airs on ABC on Sunday, May 3 at 8 p.m. EDT. Watch the promo video for “Mother” below: