A new sneak peek clip of the next episode of ABC's Once Upon a Time, featuring a pretty big revelation regarding how Elsa (Georgina Haig) is managing her icy powers.

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The new clip features Anna (Elizabeth Lail) coming back to Elsa in Arendelle of the past. The scene, featured at The Hollywood Reporter, has an air of tension as the Frozen sisters reunite.

"I was worried I would never see you again!" Elsa says, to which Anna apologizing for leaving without telling her.

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Elsa immediately asks if Anna knows any more about why their parents left for the Enchanted Forest, to which Anna essentially dodges the question with a vague answer.

"I'm still waiting for answers from a few people I met," Anna says, suspiciously, adding, "it could take a long while."

Anna then notices that Elsa has remained calm and hasn't subconsciously caused any ice crystals or frost to form in the air.

"I've been learning to control my powers when I get upset," Elsa says, enthusiastically. Anna asks how Elsa has been doing this and it is then that the scene takes a more sinister tone.

"By training with me," says a voice from behind. This voice belongs to the Snow Queen (Elizabeth Mitchell).

The Snow Queen has proven herself to be very influential in the distant past. In addition to training Elsa, she also served as a foster mother to Emma (Jennifer Morrison). The quest continues to track her down in the present during the next episode of the series.

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

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

Tags: Once Upon A Time television ABC