Once Upon a Time season 4 returns later this month, and we now know the titles of the first six episodes.

Storybrooke is freezing over in Once Upon a Time season 4, when the cast of Frozen takes over the show.

A brand new trailer for the first episode, “A Tale of Two Sisters,” was released yesterday, and we get a great new look at Elsa (Georgina Haig) and Anna (Elizabeth Lail).

We expect that the premiere episode will mainly focus on introducing the Frozen characters, with flashbacks to their fairytale past and an explanation of the threat they’ll pose to our heroes.

The first episode of season 4 will also introduce the Once: Wonderland character The Knave, played by Michael Socha. Once the Wonderland spinoff ended its run, Socha joined Once Upon a Time as a regular character.

The Frozen characters are also here to stay, at least for a little while. It seems like Elsa’s winter wonderland will continue in the second episode of the season, which KSiteTV reports will be titled “White Out.”

Josh Dallas (David) tweeted this picture a few days ago, which shows the cast seemingly preparing to go on an arctic mission. Just how cold is it going to get in Storybrooke?!

The third episode is hilariously titled “Rocky Road,” probably very intentionally referencing the Ben & Jerry’s ice cream flavour of the same name.

Episode 4 is titled “The Apprentice,” and is the first episode in which IMDb does not list the Frozen cast – although of course that can change. Who we will see is Lost and Revolution star Elizabeth Mitchell, who’s playing a mystery character somehow connected to the Frozen storyline.

Then follows episode 5, “Breaking Glass,” which does not yet have any cast information or a set air date.

And finally, series creator Adam Horowitz revealed a few days ago via Twitter that the sixth episode is titled “Family Business.” (Are the Winchesters coming to Storybrooke?!)

The premiere episode of season 4, “A Tale of Two Sisters,” airs September 28 at 8/7c on ABC.

Are you excited to see our Once Upon a Time heroes battling through what seems to be a modern-day ice age?