This is book number 4 in the How to Train Your Dragon series.
In his fourth sidesplitting adventure, Hiccup Horrendous Haddock III must rescue his best friend, Fishlegs, from the deadly disease Vorpentitis. The only cure is rare and almost impossible to find: a potato. But where will Hiccup find such a thing? He'll have to dodge the terrible Sharkworms, battle Doomfangs, and outwit crazy Hooligans if he's going to be a hero ... again.
A fast paced plot, slapstick humor, and witty dialogue enhance this exciting tale.