The young nobleman Inge is riding through Sweden, looking for his twin brother, Arild. He meets a group of gypsies who welcome him. They met Arild earlier and believe that the brother is Arild. Inge falls in love with the mysterious girl Isis.
In desperation brought on by near-starvation, Helge Roos kills his master's ox to feed his wife and baby daughter, setting off a devastating and unexpected chain of events.
Bamse's friends go on a quest to find the Thunderbell, the ingredient that makes Bamse strong. Meanwhile, the sly Reinard pretends to be a good guy to supplant Bamse as the hero of the town and win the affections of Mickelina.
In Bamse and the Witch’s daughter Croesus Vole finds gold in the beavers' dam. To demolish the dam and get the gold he tricks the witch's daughter Lova to enchant Bamse. With Bamse gone, it's up to the children to help each other to stop Croesus - but to do that they have to be friends.