|“||I tried to fight them off but there are a lot more of those Dragon Flyers than we thought.||”|
|“||After learning several Flyers followed Heather to Vanaheim, the Riders must stop them from reporting the sacred island’s location to their leader.||”|
Heather arrives on Berk, injured after she was attacked by Flyers on the way to Vanaheim. Astrid insists she stays and gets treated by Gothi while Hiccup feels torn between staying to look after his father or defending Vanaheim, which is incredibly important. He sits by Stoick's bed to air his chest and his father wakes momentarily to tell him he ought to do whatever is right. Hiccup goes to the arena to talk to the others and although Astrid and Fishlegs suggest he remain on Berk with Stoick, he insists that he can't just do nothing to defend the dragons' sacred resting place. As they are leaving, Alvin and his Outcasts arrive and promise to keep an eye on Stoick, which reassures Hiccup.
Just before arriving, the Riders discuss how dedicated the Sentinels are to their job of protecting Vanaheim and how they could have dealt with the Flyers on their own. But they are proved wrong because the island is up in flames and the Sentinels appear to be dead. They double-check for life signs but in vain. They hear grunting from a cave and Hiccup goes to investigate, armed with Inferno. Inside is an apparently injured Flyer. Hiccup shouts in anger, raising his sword and for a moment Astrid thinks he will kill the man - but instead he embeds Inferno in the sand. The twins attempt an interrogation and when the Flyer refuses to give his name, they dub him Mr. Murderous Pile of Yak Dung - who then tells them everything that had happened. It turns out that the Flyers suspect the skull belongs to the king of dragons and that the other Flyers are reporting to Johann as they speak.
Hiccup, Astrid and Snotlout leave to try and catch the Flyers. Snotlout points out the storm and Hiccup decides to fly through and meet the Flyers on the other side. Meanwhile, Meatlug starts spewing lava around the downed Sentinels, which Fishlegs thinks is to make a final resting place for them. The twins question Mr. Murderous Pile of Yak Dung about the job as a Flyer, but when the Flyer gets the wrong end of the stick and suggests they switch careers they simply laugh. Fishlegs notices the Sentinels are moving and joyously realises they're not actually dead.
As Hiccup, Astrid and Snotlout fly out of the storm, they spot the Flyers, who promptly spot them too when Hookfang flames up. Fishlegs searches Oswald's records for something on the Sentinels, which the twins mistake as ransacking - which they are more than happy to join. While they throw crates about, a Dragon Eye lens rolls out right in front of the Flyer who escapes and grabs it. He doesn't get far though, and Fishlegs gets his hands on the lens. Then Grim Gnashers show up and they hurry back to the Sentinels.
The Flyers are fighting the Riders, but they soon need to regroup. Hiccup orders they retreat back into the storm where they won't be followed but the Flyers are persistent and matters only get worse when Hookfang and Snotlout are struck by lightning. Stormfly and Toothless catch them and they take cover in an abandoned Dragon Hunter shipwreck. Outside the Flyers are trying to break in and Astrid has to encourage the self-doubting Hiccup. Then Snotlout's rant about metal attracting lightning gives Hiccup an idea.
The twins keep the Grim Gnashers busy while Fishlegs looks through Oswald's notes and he realises that Meatlug was helping the Sentinels come out of their hibernation state (caused by their injuries) all along by spewing hot lava to heat them up. Barf and Belch make an explosion to wake them up and the Sentinels defeat the Grim Gnashers. Astrid and Hiccup lure the Flyers into the storm and then throw bolas at them. The lightning is attracted to the metal on them, electrocuting the Flyers and freeing their Singetails. Snotlout joins them on Hookfang and they fly back to Vanaheim, surprised to see them alive - and even more surprised when Fishlegs reveals the Dragon Eye lens he found in Oswald's cave.
- Heather is seen without her shoulder pads.
- The Grim Gnasher makes its second appearance.
- 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
- Mae Whitman as Heather
- Nolan North as Stoick the Vast
- Mark Hamill as Alvin the Treacherous
- Gruffnut Thorston ♣
- ♣ designates a character that appears but does not speak.
- Michael Goldstrom as Johann
- Hakeem Kae-Kazim as Krogan
- James Arnold Taylor as Mr. Murderous Pile of Yak Dung
- Night Fury
- Deadly Nadder
- Monstrous Nightmare
- Hideous Zippleback
- Grim Gnasher
- Bewilderbeast (skeleton)