Five years after the Viking village of Berk has made peace with dragons, the inhabitants live alongside the once-feared creatures in harmony. The film's protagonist, now an adventurous young man, spends his days alongside his dragon companion, exploring uncharted territories and mapping the world. On one of their expeditions, they stumble upon a mysterious ice cave that is home to hundreds of wild dragons and the enigmatic Dragon Rider. This discovery leads them to a conflict with a new enemy, whose menacing agenda threatens the peace between dragons and humans.

As tensions rise, the protagonist and his closest allies find themselves at the center of a battle to protect the harmony they've fought so hard to establish. In doing so, they encounter new dragons, new friends, and unexpected revelations that challenge their understanding of the bond between humans and dragons. This sets the stage for an epic struggle that will determine the fate of both species.