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, 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 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.
When the tremors from the erupting volcano on Volcano Island begin to cause the Exterminator dragon eggs to hatch, Hiccup knows it is up to him to restore the missing Fire-Stone and save the Tribes from being wiped out.
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.
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.
"Hiccup is in hiding in the Murderous Mountains with the Company of the Dragonmark, but he is determined to become King of the Wilderwest by defeating the witch's Vampire Spydragons and steal back the King's Things from Alvin the Treacherous"--
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.