(ABC, Once Upon A Time)

But, while things were coming together for some characters, they were falling apart for others. During Emma and Hook’s trip to the past, Emma saved the life of Robin Hood’s wife and brought her back to Storybrooke, which complicated Robin Hood’s new relationship with Regina.

Belle and Rumpelstiltskin got married at the end of season 3, but Belle still doesn’t know that when Rumpelstiltskin entrusted her with the dagger that controls his power, it was actually a look-alike.

Emma and Hook also unknowingly brought back a mysterious blonde woman, who fans now know is Elsa from last year’s Disney blockbuster “Frozen.”

READ MORE: 'Once Upon A Time' Casts Its 'Frozen' Elsa

When the show returns for its 4th season on Sunday, Storybrooke will be getting an icy treatment from its newest villain. Taking place sometime after the story in “Frozen” concludes, Elsa (Georgina Haig) sends Storybrooke into an early Winter, much to the annoyance of its residents.

Elsa will be joined by her younger sister Anna (Elizabeth Lail), Anna’s fiancée Kristoff (Scott Michael Foster), Prince Hans (Tyler Jacob Moore) and Pabbie the Troll King (John Rhys-Davies).

Other guest stars will include Frances O’Connor as Belle’s Mother and Sally Pressman (“Army Wives”). Though nothing has been confirmed regarding Pressman’s role, TVLine makes a case for her playing Elsa and Anna’s late mother in flashbacks.

In a Q&A with Variety, co-creators Adam Horowitz and Edward Kitsis discussed the upcoming season, including Emma and Elsa’s surprising connection.

“Elsa has been down many of the same paths that Emma has either been down or is going down, and because of that, they’re going to find a way to bond and a way to work together,” Horowitz said.

Fans can also look forward to seeing Hook and Emma navigate their new relationship.

“We’re definitely going to show their relationship, but at the same time, we’re going to see Emma continue to evolve and question certain things about herself,” Kitsis said, adding that Hook will have his own issues this season, mostly addressing his longstanding rivalry with Rumpelstiltskin.

They also teased flashbacks from many of the characters’ pasts, going farther back in time than they ever have before.

Watch an extended preview for the new season below.

"Once Upon a Time" premieres Sunday, Sept. 28 at 8/7c on ABC.

Reach Staff Reporter Alex Reed here.