Dragons are still dragons, and as a result, they are causing mayhem in the Isle of Berk. Stoick is reconsidering allowing the dragons to roam freely on Berk. It is up to Hiccup and his friends to convince Stoick otherwise.

The peace with the dragons has put Gobber out of business, since his job was making weapons to fight dragons. Stoick asks Hiccup to help find a new job for him ... but unfortunately a change of profession does not seem to go well with Gobber.

While racing during "dragon boarding", Hiccup and Astrid cause an avalanche and end up buried in a gorge. With no one to help them, Toothless' new ability will be required to save them.

Hiccup finds an injured baby dragon, and Toothless does not warm up to the energetic newcomer. The baby's angry mother, meanwhile, makes her way toward Berk to find her lost son.

The dragons are falsely accused of vandalism and banished from Berk, leaving the island vulnerable to an attack by Alvin and the Outcasts.

Hiccup had discovered Mildew framed the dragons but has destroyed all evidence of it, therefore he must prove of their innocence in order to get them back. Meanwhile, Alvin the Treacherous of the Outcast Tribe are on the mission to raid the Isle of Berk in order to find and capture the "Dragon Conqueror".

Stoick asks Hiccup for dragon flying lessons. The preview shows Stoick trying to fly (poorly) on Toothless through Berk. Later on in the series, Stoick is seen riding what appears to be the Thunderdrum "Thornado".

Worried Stoick is disappointed in him, Hiccup heads out on a treasure hunt to prove his worth.

After Mildew poisons all the dragons on the island, he is forced to help Hiccup, Stoick, and Gobber find and capture the ferocious Scauldron in order to get the antidote.

Hiccup meets a mysterious girl named Heather.
Astrid is jealousy and suspicious when Heather seems to be after the Book of Dragons.

Heather's betrayal to Berk caused the Book of Dragons to fall into Alvin the Treacherous' hands, and Heather's imprisonment on Berk. In order to get the book back from Alvin, Astrid disguises herself as Heather and goes into Outcast Territory. Towards the end of her mission, Astrid learns and confirms Heather's true motives for helping the Outcasts.

Berk's annual festive sporting competition, the Thawfest games, is underway and all the teens are participating with the dragons for the first time in Viking history. Hiccup is determined to finally best Snotlout, who constantly gloats about being the reigning Thawfest champion, but Hiccup's successes begin to make him arrogant and boastful, much to Astrid's displeasure and disappointment.

Sudden lightning storms are endangering the residents of Berk and it is believed Thor is angry at the island. Mildew leads the superstitious villagers into blaming Toothless, "the unholy offspring of lightning and passing itself", for the lightning, leaving Hiccup to find the true answers for Thor's sudden destructive anger.

A rogue dragon - a Whispering Death - shows up in Berk, tearing up the village. He's on a mission to find Toothless and settle a score. Despite Hiccup's efforts to help, Toothless insists on facing the dragon alone. But unlike their past battle, Toothless's inability to fly my prove to be his undoing.

Dagur the Deranged visits Berk to renew a peace treaty between the Berserkers and Berk, and the dragons are put into hiding to dispel rumours that Berk is training a dragon army. But when Ruffnut and Tuffnut begin to fight, their dragon, Barf and Belch, is left out of control. The Viking youths must bring the twins back together to control their dragon and avoid provoking Dagur to war.

Caught in a waterspout, Toothless' prosthetic tail is damaged, rendering him unable to fly and thus leaving him, Hiccup and Snotlout stranded on Outcast Island. The three must work together to repair the damage, overcome the rivalry between Hiccup and Snotlout and return home to Berk before they are captured by Alvin and the Outcasts.

When Hiccup discovers Trader Johann's ship was shipwrecked in a rumored haunted bog with a gift made for him by his mother, he will stop at nothing to retrieve it.

When Snotlout and the villagers mistake dragon eggs for gems that bring good fortune, Fishlegs, who is responsible for the eggs' discovery, must take a stand against Snotlout and reunite the eggs with their Changewing mothers before they destroy Berk.

During Berk's annual Bork week celebrations, Hiccup is granted access to Bork the Bold's private and personal archives. When he finds information and a map about an island inhabited by Night Furies within Bork's notes, Hiccup is determined to bring Toothless to his family.

Mildew has betrayed the Vikings of Berk and allowed Alvin the Treacherous to kidnap Hiccup and Toothless. Astrid and Stoick must rescue them from Outcast Island along with help from a new friend.