After moving to a new town, a rebellious girl forms a bond with a wild mustang and finds a connection to her late mother’s legacy as a trick rider.

After the disastrous food storm in the first film, Flint and his friends are forced to leave the town. Flint accepts the invitation from his idol Chester V to join The Live Corp Company, which has been tasked to clean the island, and where the best inventors in the world create technologies for the betterment of mankind. When Flint discovers that his machine still operates and now creates mutant food beasts like living pickles, hungry tacodiles, shrimpanzees and apple pie-thons, he and his friends must return to save the world.

The Viking town of Berk, now enjoying its new alliance with the dragons, is preparing for its annual winter holiday of Snoggletog. However, that spirit is threatened when all the dragons, except Toothless who needs Hiccup to help him, suddenly fly away for some reason. While Astrid ineffectually tries to salvage the occasion, Hiccup decides to build Toothless a new prosthetic to allow him to fly independently, only to have the dragon take off as well. However, as the holiday approaches, Hiccup finds himself swept up to learn the dragons' secret the hard way and to find a solution to bring them home early.