|“||They say there are two ways to be fooled. One is to believe what isn't true. The other is to refuse to believe what is. Maces and Talons.||”|
|— Viggo Grimborn|
|“||Hiccup and Astrid race to stop the Dragon Hunters from tracking the Flightmare after Heather spills secrets from Viggo Grimborn.||”|
|— TV Guide|
During a battle between the Dragon Hunters and the Dragon Riders, Hiccup manages to set free shiploads of dragons, which according to Dagur is due to Ryker underestimating them. Ryker however, however, suspects someone is giving away information. He watched as Heather attacked Snotlout and the twins, causing Snotlout and Tuffnut to end up switching dragons. Hookfang and Ruffnut get caught by a net but Snotlout and Tuffnut rescue them. On the way back, Tuffnut doesn't let Ruffnut switch back.
Meanwhile, Stormfly attacks Windshear with a single spine shot to down them. Ryker confronts Heather about something not looking right. Dagur defends her and then a Hunter reports that Viggo has summoned them back to their base. Ryker leaves so Heather and Dagur discuss what they know about Viggo - that he's smart and loves the art of the kill. The two awkwardly hug and Dagur jokingly accuses her of indeed not being completely honest.
While Snotlout and Tuffnut have fun together, Astrid and Hiccup discuss whether or not to pull Heather out. Hiccup insists that they can't give up now that Heather is so close to meeting Viggo and that nothing will happen to her. Astrid is still unsure until Hiccup reasons that Heather wouldn't come even if they tried to get her out. Snotlout and Tuffnut noisily declare themselves official best friends, much to Astrid's annoyance. They retreat to a desolate cave on the Edge "where nobody can tell us off" and name it the Awesome Viking Cave Club NorthEast.
On the Hunter base, Heather and Dagur are led to Viggo's tent by Ryker. Viggo tells the story of how he used to play Maces and Talons with his grandfather. He welcomes Ryker, then a Hunter is brought in who stole dragon hide. Viggo stares the man down and then orders him to be taken away. Ryker and Dagur are told to leave, but Viggo asks Heather to stay to have a word. As they walk, a man can be heard screaming in the distance. On the edge of a cliff, he states that there cannot be a traitor among them. After saving Heather from falling off the edge, he asks her help in finding the traitor (saying he suspects Ryker or Dagur) and a Flightmare.
In the cave on Dragon's Edge, Ruffnut gains entrance by stealing the Dragon Eye, which they use to play dragon shadow puppets. She claims that Hiccup entrusted it to her, but the others don't believe her. At that moment, Fishlegs arrives and stays to chaperone the use of the Dragon Eye. Astrid and Hiccup meet with Heather, who tells them to ambush Viggo on the way to the Flightmare.
They arrive shortly before Viggo does. Ruff and Tuff are assigned the task of luring the Flightmare away. Then the Riders spot many more ships behind the one Viggo and Heather are on and when they start firing at the Riders, Heather realises Viggo set everything up. The two fight but Viggo easily overpowers her and by the time she escapes his grasp, Hunters are attacking her from all sides.
The twins attempt to lure the Flightmare, only to get splashed with the algae. They fly away, the Flightmare close behind them. The Riders are forced to both avoid the Dragon Hunters' attacks and the Flightmare's mist while Heather rescues Windshear. Hiccup tries to use the Flighmare against the Hunters by throwing algae at them. The Flightmare boards the Hunter ship, as expected, freezing the soldiers with its mist. The Hunters, however, manage to capture the Flightmare, Heather and Windshear. The Riders try to rescue her while Hiccup tries to find Viggo. Astrid is quickly forced to retreat and by the time Hiccup reaches the ship, Viggo is gone.
- 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
- JB Blanc as Ryker Grimborn
- Alfred Molina as Viggo Grimborn
- David Faustino as Dagur the Deranged
- Dragon's Edge
- Dragon Hunter Island
- Unnamed Island
- Hiccup's Prosthetic Leg
- Toothless' Saddle and Tail Fin
- Astrid's Old Axe
- Astrid's Kransen
- Heather's Axe
- Heather's Horn
- Heather's Dragon Eye Lens
- Dragon Hunter Weapons
- Dragon Hunter Ships
- Viggo's Sword