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.
After Heather's betrayal leaves the Book of Dragons in the hands of the Outcasts, the kids devise a plan for Astrid to disguise herself as Heather, sneak onto Outcast Island, and retrieve the book from Alvin and the Outcasts.
When a series of lightning storms hit Berk, Mildew claims Thor is angry at the village for allowing Toothless, a Night Fury, to live among them. Hiccup must prove Toothless's innocence as he and Stoick face an uprising against Toothless.
When Ruffnut and Tuffnut have a falling out, Hiccup and the kids must reunite them before their wayward Zippleback is discovered by Dagur the Deranged, the visiting chief from the fearsome Berserker tribe.