Dragon's Edge has been beset by small eruptions in the month following the Riders' victory over the Hunters, and with nothing left for them in the outlying islands, the Riders are forced to make the heavy decision to return to Berk. Hiccup and Fishlegs develop a mixture of Deathsong amber and Gronkle Iron to stop the lava bursts, but while gathering materials, Hiccup and Astrid discover an older Garffljorg mortally wounded, hinting that the Hunters, who are now led by the masked man who tried to abduct Hiccup and has the ability to control dragons, are continuing activity. Working together with the Gronkles and Quakens of Dark Deep, the Riders manage to stabilize the volcano, and decide to hold off on returning home to stop the Hunters once and for all.

When Hiccup is summoned to the Northern Markets to look into a curse that causes people to disappear, he is sucked down into a cavern of the fearsome Sandbuster.

Hiccup and the gang are invited to Berserker island by Daggur, only to find their dragons acting strange on the island. So when they are attacked by dragon hunters, the gang has to take them on alone, without their dragons.

When Snoutlout crashes on a mysterious island he comes face-to-face with the Wing Maidens and must rely on Astrid, Heather, and Ruffnut to rescue him.

The Riders follow the aging Eruptodon to the sacred Dragon Graveyard, but soon find themselves trapped by the fearsome Sentinel dragons who guard the graveyard.

The Outcast leader, Alvin, is kidnapped and held for ransom by bandits. They call on the Dragon Riders to request the assistance of Thor Bonecrusher.

After Astrid and Hiccup go off to an island together to retrieve a special oil, Snotlout and the rest of the riders are left to defend the edge against Krogan and the hunters.

Hiccup and the riders are on the run from the Flyers, but when they return to Berk, where Stoick is preparing for war, Hiccup is torn between his desire to get the Edge back and his unwillingness to fire on dragons.

When Stoick decides to take the battle on the Dragon Flyers to the Edge, the Riders must figure out how to trap the Flyers and take back the Edge.

After being ambushed by aggressive Slitherwing dragons on a new island, the Riders think Stormfly has been poisoned and race to get an antidote.

Tuff fakes his own death to make room for Throk, but when Ruff tries to train the Changewing that she thinks ate Tuff, a flock of angry Changewings come for the dragon.

On a search for Dagur's dad, Hiccup and Dagur encounter vicious Grim Gnashers, and Tuff's search for a missing Chicken leads him to discover she has a second family.

When Trader Yohan tells Heather her father may be alive they join forces to take her to him, meanwhile Hiccup and Daggur learn of this and swiftly head to find her to tell her the latter. When Heathers dragon is taken by Vigo and his gang its up to SnotLaut to help Heather get her dragon back and save the day. In the end we learn the real reason behind Trader Yohans treachery.