King Gregor of Dunwyn, however, has more important things to worry about. Like the party of visitors from the North. Vikings from the Island kingdom of Berk and their Dragon allies. The island has become crowded and the Vikings are looking to expand southward, or at least get some of the dragons to move out. But Gregor is wary and wants the Vikings to prove their peaceful intent. Only a marriage between Hiccup, son of the Chief, and Gregor's daughter Calla will earn the trust of both sides.
But Astrid, who doesn't want to see Hiccup married to someone who isn't her, disrupts the wedding plans, turning Dunwyn and Berk against each other. Well to be fair, it was mostly Ruffnut and Tuffnut's fault.
Buty, as both lands prepare for war, a new threat looms. The evil Duke Igthorn, sworn enemy of Dunwyn, has uncovered an ancient Gummi weapon and is moving it towards Dunwyn Castle, intent on conquering it for himself and from there, Berk. If he suceeds, he will be unstoppable.
Now, in order to stop Ignthorn and prevent a war, Calla and her friend Cavin the squire must reveal their most precious, deepest secret. Deep in the forests of Dunwyn, one tribe of Gummi Bears still lives . . . and they are our last hope.