Follows the further adventures and misadventures of Hiccup Horrendous Haddock the Third as his Viking training continues and his father leads a stranger and the Hairy Hooligans to the Isle of Skullions in search of a pirate's treasure.

"The Doomsday of Yule has arrived, and the future of dragonkind lies in the hands of one boy with nothing to show, but everything to fight for. Hiccup's quest is clear... But can he end the rebellion? Can he prove himself to be king? Can he save the dragons? The stakes have never been higher, as the very fate of the Viking world hangs in the balance!"--

Someone has stolen the Fire Egg. Now the volcano on Volcano Island is active and the tremors are hatching the eggs of the exterminator dragons! Can Hiccup return the Fire Egg to the volcano, stop the volcano from erupting, and save the Tribes from being wiped out by the terrible sword-claws of the Exterminators.