When Hiccup discovers Toothless isnt the only Night Fury, he must seek "The Hidden World", a secret Dragon Utopia before a hired tyrant named Grimmel finds it first.
As Hiccup fulfills his dream of creating a peaceful dragon utopia, Toothless discovery of an untamed, elusive mate draws the Night Fury away. When danger mounts at home and Hiccups reign as village chief is tested, both dragon and rider must make impossible decisions to save their kind.
When Toothless gets drawn away by the sudden and inexplicable appearance of female Light Fury and a new threat finds their way into Hiccups crowded dragon utopia, both human and dragon alike are prompted to begin a search for the mythical ancestral home of dragons: a hidden world thought to exist only in myth. A tale of friendship, fate, and ultimately letting go.