The show begins in the village of Berk, a cliffside village plagued by Dragons. Hiccup, son of the village chief, Stoick, introduces his home and its inhabitants (“In Berk/We’re Not Leaving – Part 1”). As everyone avoids the Dragons, Hiccup introduces Gobber, the blacksmith, and some other Recruits – Fishlegs, Snoutlout, Ruffnut, Tuffnut, Lumi, Tig, Dane, Frostbite, Sungrass, and Astrid, who is by far the most promising – who are training to rid the village of the Dragons. Astrid and the Recruits ready the catapult, supervised by Darby, as the Adult Vikings and the Recruits declare they’ll never leave Berk (“In Berk/We’re Not Leaving – Part 2”).

Hiccup wants to participate in the battle, but Frida and Gudrun remind him that he can’t swing an ax or throw a bola. Hiccup quickly produces a contraption that will launch a bola for him, and Ack wryly wishes him luck.

The Recruits help tie up the Dragons. Tig suggests that killing a Gronckle would get Hiccup a girlfriend, and Brita reminds Hiccup that only his dad, Stoick, can catch a Monstrous Nightmare. Suddenly, a Night Fury’s lightning strike hits, and Nore screams for everyone to get down! Just as Hoarck, Phlegma, and Gertrud declare that they’re not leaving, Hiccup spots the Night Fury, Toothless, and shoots the Dragon out of the sky.

Before Hiccup can celebrate, Sweeney, a Monstrous Nightmare, corners him. Stoick drops the rope containing the rest of the Dragons in order to save Hiccup, and all the Dragons go free. No one believes that Hiccup hit the Night Fury, though Astrid wounded at least seven Dragons. Stoick doesn’t believe that Hiccup has what it takes to be a Viking. Hiccup is crushed (“What A Viking Can Do – Part 1”).

Wishing for a sign, Hiccup stumbles upon Toothless in the forest, tangled up in his net. Hiccup draws his blade but can’t bring himself to hurt Toothless (“What A Viking Can Do – Part 2”). Hiccup, who now understands he can’t kill a Dragon, releases Toothless.

Back in the village, Gobber is training the Recruits. Whoever wins the training round gets the honor of killing a Dragon. Stoick tells Hiccup to train while he is gone hunting The Red Death, hoping that he can be proud of Hiccup’s progress when he returns.

Gobber begins his lesson with help from the Adult Vikings. The Recruits learn that, first and foremost, they need a shield. Then, they need to understand where the Dragon’s blind spot is located. Finally, each Dragon species has a different number of shots available (“No Turning Back”). The Recruits are disqualified against the Gronckles, Husky, Lusky, and Musky, until only Hiccup and Astrid remain. Astrid defeats Musky while Lusky sneaks up on Hiccup, who is saved by Gobber. Hiccup asks Gobber about Night Furies, confused about why Toothless didn’t hurt him, and Gobber hands Hiccup a Dragon Manual to study.

As Hiccup learns about the Dragons, they introduce themselves (“Kill On Sight”). Thunderdrums Belly and Jelly explain that they live in underwater caves and tide pools. Timberjacks Luna, Tuna, and Bruna brag about their razor-sharp wings. Scauldrons Sparky and Marky spit scalding water; Changewings Tuck and Huck spit acid; Zipplebacks Charley and Farley will bury their victims; while Skrills Lash and Dash carry their victims away. The Deadly Nadder, Blitz, declares a dance break. After each entry, Hiccup notices the same instruction: “Kill on sight.” All the Dragons admit to being afraid of Night Furies.

Hiccup returns to the forest, where Toothless is grounded. Hiccup apologizes for hurting Toothless and decides to help the Dragon. Hiccup offers Toothless an eel to eat, but Toothless is disgusted by the eel. Hiccup proposes a trade: he’ll fix Toothless’ tail if Toothless will teach Hiccup more about Dragons. The two agree to help each other (“Finally Free”).

Back in the training arena, everyone is impressed with Hiccup’s improvement, but Astrid feels overlooked. She worries about Hiccup’s success and decides to follow him (“Just Another Girl”).

In the forest, the wild Dragons sneak up on Toothless. They confront him about sharing secrets with Hiccup and fear repercussions from The Red Death. The Dragons dream of a life where humans and Dragons get along (“A Little Less Fire”).

Later, Hiccup and Toothless fly to the village using Toothless’ brand-new prosthetic tail. Stoick has returned and is very proud of Hiccup’s improvement– so much that Hiccup will be given the honor of killing a Dragon on the final exam. Hiccup tries to leave with Toothless, but Astrid follows him and discovers the truth. Before she can tell everyone, Hiccup convinces her to go for a ride (“Way Up High”). Suddenly, The Red Death calls the Dragons, and Toothless, under her thrall, takes Hiccup and Astrid to the Dragon’s Nest. Hiccup and Astrid learn that the Dragons aren’t stealing from Berk by choice – The Red Death is forcing them.

After they escape, Astrid wants to tell Stoick where the nest is, but Hiccup doesn’t want to betray Toothless’ trust. He decides to convince the Vikings without giving up the nest and makes Astrid promise to keep Toothless safe.

The next day in the arena, Stoick announces Hiccup’s battle and tells the whole crowd of villagers how proud he is of Hiccup’s success (“One Of Us – Part 1”). Hiccup faces off against Houdini, a Monstrous Nightmare, but instead of fighting, he uses the ear tickle he learned from Toothless. Houdini is spurred on by Stoick, and Toothless intervenes just before Hiccup gets hurt (“One Of Us – Part 2”). Burnthair alerts the group that Toothless is a Night Fury, and Stoick seizes Toothless and Houdini, forcing them to take him to The Red Death’s nest (“One Of Us – Part 3”).

Hiccup and the Recruits are left behind in the village. Hiccup admits to Astrid that he’s the first Viking who wouldn’t kill a Dragon – but she points out that he’s the first Viking in history to ride one. Hiccup and Astrid form a plan to help Toothless, and the Recruits train with the captured Dragons (“What A Viking Can Do/No Turning Back – Reprise”).

Stoick and the Vikings arrive at the nest (“Without Her – Part 1”) and are cornered by The Red Death, but Hiccup and the Recruits arrive just in time! The Dragons fight for their freedom (“Without Her – Part 2”). The Red Death is hurt but decides to take Hiccup and Toothless down with her (“Without Her – Part 3”). Hiccup is hit and falls off Toothless.

But he’s okay! Hiccup survives the fall and gets around with the help of a prosthetic leg. Back in Berk, the Vikings and Dragons now live in harmony (“In Berk/We’re Not Leaving – Finale”). The show ends, the lights come up for the curtain call, and the full cast sings about how to be free (“Bows”).