"White Out," the second episode of "Once Upon A Time" Season 4 premiered on Sunday, Oct. 5 at 8 pm on ABC.

In the sneak peek trailer, Elsa (Georgina Haig) ice-locked Storybrooke under her vow of finding out what happened to Anna (Elizabeth Lail). She promised, "Don't worry Anna, I will find you... Until we're together, no one leaves this town."

As Elsa desperately worried over Anna, Emma (played by Jennifer Morrison) startled her--leaving both of them trapped in an ice cave. Emma's life was put to danger. Morrison said via Entertainment Weekly, "Everything is new and scary and throws her [Elsa] for a loop, which is what causes us to be in a situation where we're trapped under ice, and clearly, the cold doesn't bother her anyway, so she's okay."

She pointed that Elsa's fear, as depicted in the original "Frozen" film, aggravated the situation. "And the problem is basically caused by Elsa being extremely fearful and causing something she didn't intend to cause. It ultimately ends up to be something that connects us, but it puts everyone in danger for a minute."

Hook (Colin O'Donoghue) and Charming (Josh Dallas) pleaded with Elsa to save Emma. When the ice broke, the latter fell in Hook's arms.

So where was Anna?

Hollywood Life noted a flashback from the time Anna showed up in the Enchanted Forest with Charming. The latter knew that she was Kristoff's (Scott Michael Foster) fiancée. But then mean Bo Peep (Robin Weigert) came to the scene wanting Charming's money. Otherwise, his farm would be taken. Anna lit hope for Charming by teaching him the art of swordsmanship.

Later on, Anna was taken by Bo Peep. Charming used his newly-acquired skills to fight Bo Peep. Anna was now back in the barn, and they meet right there. Charming thanked Anna for everything she had done for him.

Off to other characters, Regina (Lana Parrilla) was still in a state of heartbreak from Robin Hood (Tom Ellis). She isolated herself from Henry (Jared Gilmore) and the town. While Henry wanted to give his mother a basket, a crow stopped hi--leaving a note where Regina expressed her need for solitude.

Meanwhile, as Mary Margaret (Ginnifer Goodwin) was considered the town's leader, she had to take on the pressure of restarting a generator and bringing back electricity to the community. Thanks to Elsa and her powers, blackout was everywhere.

While Elsa and Emma wondered why the former's ice castle would not melt, the Snow Queen (Elizabeth Mitchell) came to show that she's got cold powers, too.

Watch the sneak peek of the episode below.