Rebecca Mader and Lana Parrilla

[Warning: This story contains major spoilers from Sunday's Once Upon a Time. Read at your own risk!]

The Wicked Witch's true identity was finally revealed during Sunday's Once Upon a Time. And while her lineage wasn't a huge surprise, we did get some insight into whyshe cast the new curse and we also welcomed back a familiar face. No, we're not talking about Ruby (Meghan Ory), who made the briefest of appearances.

In Storybrooke, Hook (Colin O'Donoghue) reveals that he left the Enchanted Forest before the new curse was cast, which is why he still has his memories. He received a note that came via a bird — a la what Snow White (Ginnifer Goodwin) would normally use — that told him to retrieve Emma (Jennifer Morrison). Unfortunately, things are getting worse in town, with some fairy-tale characters mysteriously going missing.

Once Upon a Time's Jennifer Morrison teases Emma's new predicament

Emma attempts to find out who cast the new curse, and suspects Regina (Lana Parrilla) because the curse brought her son Henry (Jared Gilmore) back to town. During a town hall meeting, Emma publicly accuses Regina, but it's all an act so the culprit will believe the heat is on someone else — the Wicked Witch (Rebecca Mader) is discreetly in attendance, after all.

Instead, the duo teams up to uncover the truth. Regina attempts to create a memory potion like the one that was given to Emma. When it doesn't work, she and Emma decide to leak the info that they were successful in order to smoke out who cast the curse.

Unfortunately, the Wicked Witch is already planting the seeds of her plans by befriending Snow White as her alter ego Zelena. She offers her help and services when she sees that Snow White is nervous about her impending child, telling Snow that she was a midwife in their old land. So, she's trying to steal the baby? Ruh-roh. She's also turning those missing fairy-tale characters into flying monkeys, so let's not put anything past her. 

Regina casts a blood spell on her office, so whoever is behind the curse will be trapped. It's a spell she also used on her castle back in the Enchanted Forest. But when Regina and Emma move in, Zelena is able to escape, which can only mean one thing.

Lightning Round 11: Once Upon a Time bosses answer your burning questions

Back in the Enchanted Forest, with the help of Belle (Emilie de Ravin), the group deduces that the Wicked Witch has taken over the castle. Though Regina seems to know facts about Oz, she says she's never met the Wicked Witch before. Regina and Robin Hood (Sean Maguire) sneak into the castle through an underground tunnel with plans to lower the protection spell so Charming (Josh Dallas) & Co. can attack.

But Regina doesn't care about the Witch, only gaining access to the castle so she can make a sleeping curse for herself so she doesn't have to live with the pain of losing Henry. But the Wicked Witch interrupts her with the big secret we've all been waiting for: The reason Zelena could break the blood spells is because she is Regina's half-sister. Angry over her sister having the better life, Zelena plans to take everything away from her, which was partly why she cast the new curse. But now Regina has a reason to live because she has someone new to destroy.

Many fans had suspected this is where the story was going, so it's not too big of a shock. Zelena is Cora's (Barbara Hershey) first child. But the question is: Who's the father? Maybe it's Rumplestiltskin (Robert Carlyle), who was also her teacher.

Back in present-day Storybrooke, the group deduces that the Wicked Witch is behind this new curse, what with the flying monkeys and the cloud of green smoke. But Zelena has a bigger secret lying in wait: Rumple is still alive and is her prisoner in Storybrooke — but it seems like he's gone back to the old crazy Rumple from the Enchanted Forest. Yikes.

Were you surprised by the familial reveal? Does this make Regina the Wicked Witch of the East? Hit the comments with your thoughts!

Once Upon a Time airs Sundays at 8/7c on ABC.