Emma (Jennifer Morrison) and Regina (Lana Parrilla) team up for the common good on the next episode of ABC's Once Upon a Time.

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ABC has released a plot synopsis for the next episode of Once Upon a Time, which is titled Lily. Obviously this episode will be delving into the history of Lily (Agnes Bruckner), with Emma and Regina attempting to reunite her with her mother, Maleficent (Kristin Bauer van Straten).

"Emma's potential for darkness is looming over everyone, but when Emma realizes Maleficent's daughter Lily is in fact her closest friend from her foster care days, she resolves to find Lily and reunite her with her mother," the synopsis reads. "Regina joins forces with Emma and together they set out to track down Lily and to warn Robin [Sean Maguire] about Zelena [Rebecca Mader]. However, neither of them is prepared for the harsh realities they'll encounter in the outside world."

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Back in Storybrooke, Mr. Gold (Robert Carlyle) will encounter a "crisis" concerning Belle (Emilie de Ravin).

As for this week's flashback, fans will get to see young Emma and Lily in foster care.

"Things are looking up for young Emma with her new family until Lily's appearance threatens to destabilize everything," the synopsis reads.

Notably, both Mader and Maguire will be seen in the episode, suggesting that Regina may be reunited with her true love Robin again.

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

Watch the promo for the next episode of Once Upon a Time here: