|“||While on night patrol, Stoick is ambushed by the Flyers and gravely injured, leaving Hiccup torn between his duties as a son and as the Riders’ leader.||”|
Stoick and Skullcrusher venture alone for an evening patrol of Berk. They are suddenly caught off guard as several Dragon Flyers ambush them and both Stoick and Skullcrusher are severely injured in the attack. Luckily, the A-Team arrived, fends off the Dragon Flyers, and rescue them to safety. When word spreads of Stoick's unconsciousness due to his injuries, Hiccup races home and is devastated to see his father's condition, resulting in him being too grief-stricken to notice his fellow Riders. With no chief to take care of the village, the Riders and lead Vikings congregate as they discuss the fate of Berk with no leader. Spitelout and the Vikings agree that Hiccup must take up chiefdom in Stoick's absence. Gobber and Astrid attempt to deliver the request to Hiccup. However, Hiccup strongly rejected the offer, as he reasoned that he needs to be with his dad until he hopefully recovers.
Hours later, Hiccup has trouble sleeping as his father’s words echo in his dreams and decides to stay in the Great Hall, as he is torn as to what his response should be in the aftermath. The Riders also arrive in the Great Hall to comfort him. Astrid tries to dissuade Hiccup from believing that he's to blame for what has unfolded but the Twins argue otherwise, claiming if the Riders never left he would've kept his father safe but on contrast Berk would've gone into a state of "full Loki" and end up in the same situation with Johann. They envision their alternate reality, where they go back to the time where they first began deploying pranks on Berk and soon escalates that eventually, everyone in the entire village pulled pranks on each other, leaving Berk defenseless, and it's oblivious that Johann and his lackeys were able to take over Berk in a single blow.
Fishlegs suggests a different view of what would happen if they all stayed, whereby Berk eventually grows to immerse themselves in a state of peace and tranquility in which wars will be pointless resulting in relations with Johann, Viggo, and Dagur. But Snotlout interjects that in the end, they will eventually turn on against each other, as he believes it's in a Viking's nature. He then presents his own point of view where he believes that he'll eventually be promoted to a legendary Official Weapons Inventor, where he wields his greatest super-weapon and becomes a warrior revered by all of Berk, including his father and Astrid.
All their stories are viewed by the Riders to be ridiculous and they dispute which is the more likely scenario. Frustrated, Hiccup snaps, telling them all their predictions are pointless and instead that all the events that led up to the present are because of his fatal shooting of Toothless years ago, and he blames himself believing that decision endangered his father. He walks out of the Great Hall in despair. For a long moment, Hiccup isolates himself sitting at a cliff edge at night. Toothless joins him, despite hearing that his Rider seems to regret his actions that resulted in their friendship. Hiccup apologizes, reassuring Toothless that he never meant it to be true. Astrid follows and tries to talk some sense into him. Astrid asks Hiccup to envision himself what would he be like if he never did shoot Toothless in the first place.
Then the scene flashed back to the moment in the first film, where a young Hiccup's moments away from pulling the trigger. When Toothless came into his range, he fired, but the bola missed him. Then history changes from that point on, as a few years later, Hiccup still worked at Gobber's blacksmith shop, with the only companion being Fishlegs, who's now interested only in studying plant life, and that Snotlout's admired by Stoick for his record of killed dragons, and he prepared to woo Astrid in marriage. Then Stoick confronted Hiccup, and he demanded that he finally made his first dragon kill out at the forests, and that he can't return unless he's done so. At the cove, Hiccup awaited for the dragon he'll confront, which it turned out to be a Night Fury. While busy taking a drink, Hiccup tried to capture it with a net, but he clumsily failed. Fortunately, Toothless suddenly got tangled up in the net, enough to be immobile. When Hiccup took out his knife and lifted it, he still couldn't bring himself to kill it, so he freed it. Just when the pair began to go their separate ways, a Whispering Death emerged from the ground, and it attempted to attack Hiccup. Then Toothless dove in and he rescues Hiccup, but in the process, Hiccup latched on Toothless's body while Toothless prepared to take off with the Whispering Death in pursuit.
Their chase attracts the attention of Stoick and Gobber, who is shocked to see that Hiccup is riding the legendary Night Fury and they set foot to save him. But one of Toothless's tail fins got shot by the Whispering Death, rendering them flightless, and then they crashed back into the cove. Now Toothless's momentarily unable to fight back, and the Whispering Death prepared to seize the moment. Then Hiccup bravely attempted to divert the dragon's attention to him, but he got brutally struck with the Whispering Death's flames, and he was unconsciousness. By seeing his bravery, Then Toothless tried to avenge him, as he protected Hiccup from being finished by the Whispering Death. Then help eventually arrives, as Stoick and Gobber overpowered the Whispering Death, and it left in defeat. Then Stoick's prevented from killing Toothless, when he realized that he kept his son safe. A few days later, Hiccup recovered but with a prosthetic leg due to the attack, and that Toothless's allowed to enter Viking society with his tail fin repaired by Gobber. Then Stoick presented Toothless as not a threat, but a hero to Berk, then Hiccup and Toothless were praised by the villagers including Astrid. Then Stoick finally declared an end to the hostilities to all the dragons.
Then the scenario finished, and Hiccup and Astrid realized that the other Riders were listening in, with the Twins complaining why did the entire scenario still had the same results as it did in their own reality. Then they clarified that no matter how things have gone, Hiccup, Toothless, and the rest of them are bound to be in the state they're now. Then Hiccup's finally relieved of his self-loathing as he accepted that none of his actions are to blame. Then he gone to have one final visit with his dad, trying to assure him that he won't give up, and that he'll continue to fight back against Johann, and he wished that he pulled through his condition, for the village and his sake. Just as he prepared to leave, Astrid interrupted and she urgently requested Hiccup outside. Then Hiccup found Heather injured in Fishlegs’s arms, and then she brought Hiccup some dire news that the Dragon Flyers have invaded Vanaheim.
- 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
- Nolan North as Stoick the Vast
- Chris Edgerly as Gobber the Belch
- David Tennant as Spitelout Jorgenson
- Lucas Grabeel as Gustav Larson
- David Faustino as Dagur the Deranged ♣
- Mae Whitman as Heather
- ♣ designates a character that appears but does not speak
- Barf and Belch
- Krogan's Singetail
- Toothless' Nemesis
- Night Fury
- Deadly Nadder
- Monstrous Nightmare
- Hideous Zippleback
- Terrible Terror
- Whispering Death
- This is the second time a flashback from the first movie appears in the series. The first time was during "Viking for Hire".
- Toothless's Nemesis makes its first appearance since "What Flies Beneath", although only in a "what if" scenario.
- The "what if" scenario for Snotlout and the Twins are very similar to the stories they tell in Burning Midnight.
- This is the first time Toothless is seen with both of his tail fins intact.
- Snotlout's invented weapon had already been invented, since Gobber had one in his weapons cart in "Viking For Hire".
- The Whispering Death's fire should not have destroyed Toothless's left tail fin in Astrid's "what if" scenario, as dragons are fireproof.