On Christmas Eve, Lena arrives at her uncle's with the bear she tamed. Her uncle invites her to join them in the barn, because the trolls break in every Christmas Eve, to hold their feast in the hall.
Lena would have none of it. She went to sleep inside. And so did the bear.
The trolls arrive --elaborated in details. And it starts with singing and dancing and drinking and eating, but it doesn't stop there.