Something Rotten on Berserker Island is the third episode of Dragons: Race to the Edge, Season 5. It was released on August 25, 2017.
The Riders are on their way to Berserker Island after receiving an invite from Dagur the Deranged to attend an apprentice graduation ceremony. The Riders are warmly greeted by Heather and Dagur, although Dagur continuously irritates Snotlout by repeatedly calling him an incorrect name. While being escorted throughout the village, Hiccup is surprised to learn that Savage is a member of the inhabitants, to which Dagur explains that he personally took him in. Strangely, as they fly overhead at the village, their dragons begin to feel agitated, so Dagur takes them to a nearby stable at a high point overlooking the village. Once the dragons are settled, Dagur introduces, to which he claims, one of the Berserker's greatest graduating apprentices, Gustav Larson. The Riders reveal their disbelief, especially Snotlout, who envies his position. Regardless, Dagur seems to greatly admire Gustav after claiming to be devoted to Berserker culture that resulted in his graduation to be two weeks early. Gustav invites the Riders for a tour of the village, but shortly after leaving, a bottle is seen thrown into the stables, releasing gas that severely weakens the dragons, who are then locked inside by unknown assailants.
The Riders are disappointed to find that Berserker Island is not what they had expected to be like and that Gustav's plans for the ceremony and contributions to the village are of poor effort. Afterwards, the ceremony commences, Dagur delivers his speech of Gustav's graduation, just as Hiccup and Astrid notice suspicious activity by the nearby Berserker guards. Suddenly, Dagur is pinned down by two of his own men, as Savage enters and stages a coup of overthrowing Dagur as chieftain, with many of the Berserker solidiers supporting. The Riders flee and abandon Dagur, as the Berserkers give chase. Heather leads them to a hiding spot, where they gather a plan, Hiccup and some of the Riders decide to free their dragons from the stables while Snotlout and Gustav are assigned to help Dagur escape from the village's prison by using the Maze of Caves under the island as a shortcut.
Dagur asks why would Savage betray him after he was granted to live peacefully on Berserker island, Savage angrily retorts that he always hated Dagur after taking sides with the Riders, and Dagur is thrown into his cell. At the Maze of Caves, Gustav continues to boast to Snotlout that he was chosen because he had great potential, but Snotlout remains adamant that it isn't true. As they venture through though, Gustav struggles to hide his fears of the cave, much to Snotlout's annoyance.
At a safe point near the stables, the Riders observe that the stables are heavily guarded and need a different approach to free their dragons. The opportunity comes when Ruff and Tuff, unfazed, calmly approach the Berserkers and solely give their attention. Seizing the moment, the Riders are able to swiftly sneak in near the stables and open the doors as their dragons drive the Berserkers away.
The caves eventually lead Snotlout and Gustav towards a well, at a close distance with the prison cells. Snotlout assigns Gustav to rescue Dagur as he creates a diversion, but Gustav tries to excuse himself that he feels much better to do it with his dragon, but Snotlout frustratingly points out that they have to do it themselves without their dragons. Snotlout successfully diverts the guards away, but when Gustav attempts to sneak in, he clumsily reveals himself to another Berserker and is thrown in the cell with Dagur. Fortunately, Snotlout manages to outsmart the guards and liberates both Dagur and Gustav. However, he is angered even more when Dagur seems oblivious to the fact that Gustav ruined their plan and that Snotlout did all the rescuing.
Hiccup and the Riders are unable to ride their dragons through the village as they become extremely disconcerted if they came anywhere near. Unable to find out the cause, the Riders arm themselves to combat the Berserkers guarding Savage. Meanwhile, Dagur, Gustav, and Snotlout are pinned down by large numbers of Berserkers. The three of them decide to take the risk of fighting their way through, but Gustav submits to his fears and confesses that he faked his achievements as a Berserker apprentice and refuses to fight. Snotlout points out that he was right all along, Dagur suddenly shoves him away from Gustav and reveals to him that Gustav was only on Berserker Island because Stoick needed a break from him and that the ceremony was made up. After this, Snotlout and Dagur decide to take on the Berserkers by themselves.
At the village, a skirmish ensues between the Riders and the Berserkers, supported by Toothless atop the cliff. They managed to push through to Savage’s headquarters and overpower the remaining Berserkers. Sensing defeat, Savage grabs Heather and threatens to kill her, demanding they lay down their weapons. But Snotlout and Dagur arrives just in time, with Snotlout knocking out Savage, and Dagur able to regain his position as chief.
With order restored, Dagur continues the ceremony the next day with Gustav expecting to be awarded. Snotlout watches in envy, but to his surprise, Dagur announces that the trophy goes to Snotlout, commemorating his acts of heroism during the coup. Snotlout enthusiastically grasps the trophy with a firm belief that Dagur finally admires him. On their way home, Snotlout continues to be proud for being titled hero in Berserker Island, but when he reads the inscription on the trophy, Snotlout angrily tosses the trophy in the ocean as Dagur intentionally wrote his name as Snotknuckles.
- A running gag throughout the episode is Dagur always getting Snotlout's name wrong.
- Dagur calls him 9 different names- "Snothat", "Snotpocket", "Snotlip", "Snothole", "Snotface", "Snotrag", "Snotpit", "Snotrider", and "Snotknuckles".
- Dagur's throne looks an awful lot like the iconic Iron Throne in the series Game of Thrones.
- When Dagur called Snotlout "Snotface", it references the name of Snotlout's book counterpart.
- The Red Death is mentioned, referencing the first movie.
- The episode "The Eel Effect" is also referenced when Fishlegs reminds Hiccup of another time Toothless went "crazy".
- Jay Baruchel as Hiccup Horrendous Haddock III
- America Ferrera as Astrid Hofferson
- Christopher Mintz-Plasse as Fishlegs Ingerman
- T.J. Miller as Tuffnut Thorston
- Andree Vermeulen as Ruffnut Thorston
- Zack Pearlman as Snotlout Jorgenson
- Mae Whitman as Heather
- David Faustino as Dagur the Deranged
- Paul Rugg as Savage
- Lucas Grabeel as Gustav Larson