Maleficent and Lily
Maleficent and LilyScreenshot/Youtube

Season 4 episode 20 of "Once Upon a Time" marks the last episode before the two-hour finale. "Mother", which will be aired on Sunday, 3 May, will deal with the mother-daughter relationship in the abc show; but which one?

While the relationship between Emma and her mother Snow White is rocky, Maleficent and her daughter Lily have a lot to catch up on after living apart for 30 years. According to the promo of "Mother", Cora will also make an appearance, meaning the episode could be about the misunderstood love for her daughter Regina, as it can be about Zelina and her unborn child with Robin.

The previous "Once Upon a Time" episode, titled "Lily", gave an insight into the friendship between Emma and Lily and how the latter always made bad choices, thanks to a wrong decision made by Snow White (Ginnifer Goodwin) and Prince Charming (Josh Dallas). Although Lily (Agnes Bruckner) had insisted that she make those pay who had separated her from her mother, Emma (Jennifer Morrison) was able to temporarily placate her, at least until she and Regina (Lana Parrilla) tracked down Robin Hood (Sean Maguire).

In the promo for "Mother", Emma is seen introducing Maleficent (Kristin Bauer van Straten) to her daughter, after which they are seen sitting at Granny's Diner, planning on how to make Snow White and Charming pay for what they did. Therefore, the upcoming episode most obviously point towards the wronged mother Maleficent.

However, scenes from Storybrooke show Regina and Cora's (Barbara Hershey) past. Hence, the episode could be about this mother-daughter duo too. Meanwhile, Regina's jealous sister, the Wicked Witch of the West, is trying to ruin Regina's happy ending by posing as Robin Hood's wife Marian (Christie Laing). She is not pregnant with his child, meaning "Mother" could very well be about her as well.

After Emma learnt the truth about what happened to Maleficent's baby, she had been treating her parents very coldly. However, with each passing episode she is learning that every parent is capable of going to extreme lengths for their children. Will "Mother" make her realise that Snow White, when it came to protecting her daughter from extreme darkness, she really had no choice?

Find out in Season 4 Episode 20 of "Once Upon a Time" on Sunday, 3 May at 8.00 pm (EST) in abc.