Trailers have given away some more details, starting with what Elsa and Anna will be forced to deal with as the film unfolds.
In one trailer, a young Anna and Elsa are told about an enchanted forest which has been cursed, and as they grow up the memory of this comes back to them.
Elsa then begins to hear singing from somewhere, and realises that, when the weather changes and makes their home of Arendelle a dangerous place, the singing must be calling her out to somewhere new.
She and Anna, along with Kristoff, Sven and Olaf, must head into the mountains to discover where the voice is coming from, and how they can save Arendelle.
source: express.co.uk