Hiccup cautiously accepts Alvin's help on a mission to rescue Stoick from Dagur's clutches. The dragon riders, the Berserkers and the Screaming Death all converge on Outcast Island, for a war that may decide the fate of the archipelago.
When Stoick has a portrait of himself and Hiccup painted for the collection in the Great Hall, Hiccup ends up depicted as a strong, burly Viking, not his usual skinny self.
With Bork Day, the annual holiday celebrating the village's history, fast approaching, Stoick bestows Hiccup with all of Bork's notes and studies on dragons.
As the dragons become more comfortable as a part of Berk society, the livestock are becoming less comfortable - fire-breathing predators are, after all, around every corner. As a result, Berk is running low on eggs, milk and other food supplies.
The kids go on a dragon survival training mission to Dragon Island, where they encounter Dagur, the Berserker Chief, who has become obsessed with hunting the Night Fury.
Hiccup discovers that the town's water shortage has been caused by the Outcasts' plan to hide Whispering Death eggs under Berk, which soon hatch and tunnel underthe island, threatening the villagers.