|“||I think it might be time to head back to Berk. Viggo and Ryker are gone. The Dragon Eye is destroyed. Even Mother Nature is telling us to go.||”|
|“||With their enemies defeated and the volcano erupting on Dragon's Edge, the Riders decide to return to Berk but Hiccup discovers that the Dragon Hunters are still out there.||”|
Three months after the last eruption, the Riders are awakened to violent tremors from the island's volcano. The Riders try their best to clean up the lava by sealing the holes spewing lava with Gronckle Iron. Although they manage to wipe out the lava, most of their base is devastated. This convinces the Riders, especially Snotlout, that it's time to abandon their base after Viggo and Ryker's demise. Hiccup reluctantly accepts, but states they could only leave once they made the island stabilized for the dragons living there. Hiccup and Fishlegs devise an idea to mix Gronckle Iron and Death Song Amber. After many attempts, they managed to combine the two as an effective stabilizer to lava spewage. The formula successfully works after testing but Fishlegs says that there isn't enough Gronckle Iron and Death Song Amber to stem the lava. Hiccup assigns Ruff, Tuff, and Snotlout to gather Gronckles at Dark Deep, Fishlegs is to stay and gather the ingredients, while Hiccup and Astrid volunteer to gather amber at Melody Island.
As they explore the grounds of Melody Island, Hiccup and Astrid notice that a Death Song hasn't made any sign of appearance yet, which is strange because they are not stealthy dragons. Suddenly, a shriek from a Death Song pierces the silence and the pair prepare to calm it down as it sounds agitated. However, they swiftly realise that something is wrong, as the creature seems exhausted from its outburst, and drops to the ground in fatigue. Hiccup approaches the dragon and realizes it is severely wounded and exhausted, and the two then familiarize with horror that the dragon is the grown up Garffiljorg. Astrid notices arrows originating from Dragon Hunters stuck in his body. With Viggo and Ryker believed to be dead, the two realize that someone else is leading the remaining Dragon Hunters and that the other Death Song is nowhere to be seen. Astrid draws the conclusion that it could have been captured... or worse.
Meanwhile, three Deadly Nadders fly off to inspect a strange noise, only to realize too late that it was a trap and they are captured with Death Song amber by a Death Song. Krogan, the new leader of the Hunters, searches the area with the downed dragons, looking for a particular dragon. He eventually finds it, a green Singetail. The Hunters are shocked as Kragon manages to calm the dangerous dragon, and orders the Hunters to find as many other Singetails as they can.
At Dark Deep, the Twins and Snotlout discover that the Gronckles are surrounded by three Catastrophic Quakens. With this observation, the Twins realize that the dragons are living in symbiotic harmony, and explain this to a confused Snotlout. This proves problematic as the Catastrophic Quakens are extremely hostile toward outsiders, guarding the Gronckles they need. The Twins devise a different approach, remembering that the Hunters used vibrations to control the Quakens, they ask Snotlout to do the same. Snotlout agrees, not knowing that the Quakens don't respond to vibrations anymore and the Twins expect to ditch him with the Quakens at the last moment. Once Snotlout is able to catch the attention of the Quakens, the Twins manage to lure the Gronckles away from Dark Deep.
Back at Melody Island, Hiccup finishes pouring the last batch of Death Song Amber, Astrid finishes cleaning up Garff as much as she can but the dragon is still seriously hurt, coated in deep rakes and scratches. Astrid realizes that Garff may not last long and decides that she and Stormfly will stay with him to comfort Garff until he passes over, Hiccup reluctantly accepts to leave with the supply of Death Song Amber and return to the Edge alone.
Hours later, the Twins arrive with the Gronckles and Fishlegs wastes no time in feeding the Gronckles the specific rocks for Gronckle Iron, using the Twins' boar pit for Gronckle Iron storage, much to the Twins' frustration. Soon after, Hiccup and Toothless arrive with the Death Song amber and they hurriedly mix the two main ingredients as the volcano has started to erupt again.
The Riders manage to seal the remaining vents for good, with the last one being at the volcano's peak. The last vent intensely erupts with lava, so in a team effort, they dump all the remaining supply of the combined Gronckle Iron and Death Song Amber to seal the vent. However, tremors build up in the volcano, causing a rock avalanche that traps the Gronckles from Dark Deep. The Riders attempt to dig through to free the wild dragons but realize they don't have enough time, as a huge flow of lava is headed towards the rock pile. Fortunately, Snotlout and Hookfang return with the Catastrophic Quakens in pursuit. The Quakens discover that their boulder class brothers are trapped in the rock pile and assess the situation quickly by creating a new crater at a safe distance, diverting the lava flow. With the volcano stabilized, they immediately liberate the Gronckles and head home for Dark Deep all together.
The next day at Melody Island, it is revealed that Garff narrowly escapes death and is making a recovery. Hiccup and Astrid realize though that other dragons are still endangered now that they know the hunters are still active. Hiccup asks that the Riders stay at the Edge in spite of knowing they want to go home, but to his surprise, most of the Riders never wanted to go back, Snotlout relents and agrees to stay too.
During the night at the Hunters' island, Krogan enters the arena and approaches a steel cage containing a violent Singetail with the Hunters watching nearby. He signals a Hunter to open the cage as he attempts to ride the dragon. The Singetail violently tries to fling Krogan off of his back but Krogan stubbornly holds on, and soon the Singetail begins to show submission.
- The episode "Not Lout" is referenced when Tuff reminds Astrid that Dragon Root requires a lot of light to be able to grow.
- The episode "Dire Straits" is also referenced when Fishlegs remembers how Death Song amber holds up under intense pressure. Hiccup's diving helmet is also seen again.
- The episode "Between a Rock and a Hard Place" is referenced as well when the twins remind Snotlout that the vibrations of a heavy metal weapon hitting the ground is the best way to get a Catastrophic Quaken's attention.
- Johann mentions the famous defeat of the Byzantine Empire under Emperor Nicephorus by the Bulgars at the Battle of Pliska in 811. This is of course an actual battle that occurred out of the universe, and is most likely just added in for a reference, rather than it having been an actual event relating to the Franchise.
- Jay Baruchel as Hiccup Horrendous Haddock III
- America Ferrera as Astrid Hofferson
- Christopher Mintz-Plasse as Fishlegs Ingerman
- T.J. Miller as Tuffnut Thorston
- Andrée Vermeulen as Ruffnut Thorston
- Zack Pearlman as Snotlout Jorgenson
- Michael Goldstrom as Johann
- Barf and Belch
- Garff's Adoptive Father
- Enslaved Quakens
- Ambered Singetail
- Night Fury
- Deadly Nadder
- Monstrous Nightmare
- Hideous Zippleback
- Death Song
- Catastrophic Quaken
- Dragon's Edge
- Dark Deep
- Melody Island
- Unnamed Islands
- Hiccup's Prosthetic Leg
- Astrid's Kransen
- Gronckle Iron
- Death Song Amber Glasses
- Dragon Hunter Weapons
- Dragon Eye (mentioned)
- DreamWorks TV Dragons: Race to the Edge Episode Guide. (Copyright 2018) DreamworksTV