'Once Upon a Time' reveals what happened to Maleficent's child

Warning: This story contains major spoilers from Sunday's episode of Once Upon a Time.

Many Once Upon a Time fans have long suspected the identity of Maleficent's daughter was Emma's (Jennifer Morrison) one-time childhood comrade Lily (Nicole Munoz)—and on Sunday night, they were proven right.

It wasn't actually that far-fetched a theory since executive producer Adam Horowitz revealed in February that an upcoming episode is titled "Lily," following the tease that the titular character would eventually return. But the way the Once bosses plotted her return and connection to Emma was quite brilliant.

During Sunday's episode, Snow White (Ginnifer Goodwin) and Prince Charming (Josh Dallas) were pointed in the direction of the Sorcerer's Apprentice (Timothy Webber) by the Author (Patrick Fischler)—more scoop on him in next week's issue of Entertainment Weekly. The Apprentice offered the Charmings a way to ensure Emma would not be swayed toward the dark side by putting her darkness into another being with a blank slate. The Charmings then stole Maleficent's (Kristin Bauer Van Straten) dragon egg with the promise they would return it—but since nothing ever goes as planned on Once, the Apprentice banished the egg to the real world, much to the Charmings' chagrin, especially once they saw the egg housed a human baby and not a monster.

Fortunately, the baby found an adoptive family in the real world, and it's revealed that the child has a star birthmark on her wrist, just like the one young Lily and Emma bonded over as children. "When we introduced Lily in episode 5 of the season, we had a big plan for her and now we're paying it off," Horowitz tells EW. "There was no accident to the idea that we showed her birthmark. We wanted to establish a connection and something special about her early on. One thing we wanted to do was take both halves of the season and have connective tissue between the both of them."

Though it seems unlikely that the daughters of heroes and villains would happen to meet in the real world, executive producer Edward Kitsis promises there's a good explanation that will be explored further in coming episodes. "Episode 16 does show their connection, which is [Lily's] carrying around Emma's darkness and Emma is carrying around her lightness," he says. "Even in that moment when the parents take her away, they've connected them forever."

While Lily didn't appear to be too dark of a child when she initially crossed paths with Emma, years have passed and much could have changed. "When we met Lily, she didn't seem like a bad person, but she was lying to Emma," Kitsis points out. "Lying came second nature to her. What we're going to see is: We're all faced with choices and it's the choices you make. What happened to Lily and how she grew up is something we're going to really explore."

As Emma faces the truth about what her parents did, she'll be determined to right their wrongs. But don't expect her to necessarily look to the Author to rewrite the past. "Sometimes you can change the past by changing the present," Kitsis says. "They thought they killed the baby and now we realize Lily is out there, so the next step is someone has to reunite that child with Maleficent. Does that erase what they did in the past? No." Adds Horowitz: "We're talking about redemption, not time travel."

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