One day, Ullak forgets her grandma's warning about playing on the ice pans and is suddenly kidnapped by a sea monster.

Ullak is brought to Sanna, the ruler of the seas and all the mammals in it, at the bottom of the sea. Together they visit different Arctic sea animals and learn all about them. Ullak is having a lot of fun exploring underwater, but it's getting late. Will she be able to convince Sanna to help her find her way home?