Chronicles the adventures and misadventures of Hiccup Horrendous Haddock the Third as he tries to pass the important initiation test of his Viking clan, the Tribe of the Hairy Hooligans, by catching and training a dragon.
Hiccup, stranded with Toothless on the Beach of the Broken Heart and being hunted by an old enemy, faces Ug the Uglithug, Berserks, and Scarers and tries to save Fishlegs from the Beast.
Recounts the further escapades of Hiccup Horrendous Haddock the Third as he continues his Viking training during which he escapes from a boatload of Roman soldiers and searches for his kidnapped dragon.
When an uprising of nasty dragons begins, it becomes clear that their main target is Hiccup Horrendous Haddock III, leaving the scrawny Viking no choice but to fight to defend his archipelago.
Hiccup, the reluctant Viking hero, has three months, five days, and six hours to discover America, return to Berk, save his father, battle Polarserpents, and win the annual Inter-Tribal Friendly Swimming Race.
When his best friend Fishlegs is stricken with Vorpentitis, Hiccup Horrendous Haddock III must outwit Sharkworms, Doomfangs, and Hooligans to find a potato--the rare cure for this deadly disease.
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.