When Alvin the Treacherous captures the Skrill, Hiccup, Ruffnut, and Tuffnut go undercover to discover that a truce is in the process of being formed between the Outcasts and the Berserkers to invade Berk with the Skrill as their weapon. Dagur is giving Alvin the support of his vast fleet in exchange for the Skrill, but the truce is uneasy. The trio must now flee to release the Skrill from their control before the truce can be settled.
Tropes
- Bavarian Fire Drill: How Tuffnut convinces enemy soldiers he's one of them.
- Becoming the Mask: Played for Laughs; after going undercover, Tuffnut forgets whose side he's on while reporting to Hiccup.Tuffnut: The plan is to smash those dirty Berkians to pieces, with both fleets! It's gonna be awesome.Hiccup: Uh, you do realize, we're the Berkians?Tuffnut: Oh, right. Still gonna be awesome!
- Combat Pragmatist: Dagur. After he loses in hand-to-hand combat to Alvin, he then sets the Skrill on the latter, forcing Alvin to jump ship and then suffer electrocution.
- Continuity Nod:
- Dagur's hatred for his father comes back during the dinner with "Buffnut". He specifically grows irritated by the constant smacking he hears because he hated when his father smacked while he ate.
- Toothless grunts as a thunderstorm forces him and Hiccup to camp, likely remembering a lightning bolt shooting him and Hiccup out of the sky.
- Didn't Think This Through: Tuffnut's tree disguise, not only can he not see what he's spying on, but bark beetles get in his pants.
- Disney Villain Death: Alvin is presumed dead after jumping into water that was electrified moments later. Of course, they Never Found the Body.
- Evil vs. Evil: Dagur and Alvin inevitably come to blows by the end of the episode. Dagur wins.
- Foil: Hiccup and Toothless vs Dagur and the Skrill; the former are best friends, trust each other to death, and Hiccup rides Toothless. Meanwhile Dagur intends to enslave the Skrill, sees it only as a weapon, and uses specialized reins to hang underneath it like he's parasailing.
- The Guards Must Be Crazy: None of the Berserkers know who Tuffnut is or what he looks like, not even Dagur, who has been on Berk and fought the riders twice now.
- Hall of Mirrors: Hiccup uses his and Toothless's reflections in the ice cave to trick the Skrill into stunning itself long enough for the twins to refreeze it.
- He Didn't Make It: Ruffnut says this about Tuffnut when Hiccup asks where he is. Turns out he's just hiding in a tree.
- Hoist by His Own Petard: Dagur is defeated by stepping into a puddle while he's holding the Skrill's reins, and gets electrocuted for his trouble.
- Most Definitely Not a Villain: Inverted, Tuffnut pretends to be "Berserker Buffnut" in order to infiltrate Outcast Island.
- No One Gets Left Behind: Why Hiccup stays out looking for the twins after they went MIA in the last episode.
- Oh, Crap!:
- Hiccup and Tuffnut when they find the Skrill missing.
- Alvin when treading water right when Dagur sets the Skrill on him.
- The Unintelligible: Anyone hit by lightning, though special note goes to Mildew, who is rendered unable tell his allies that "Buffnut" is actually from Berk.
- Villain Team-Up: Alvin and the Outcasts, Dagur and the Berserkers, and Mildew have all teamed up and are planning to use the Skrill to destroy Berk.
- Whole-Plot Reference: Dagur plays the Azula to Alvin's Long Feng — two villains (one older, one younger) who are on opposite, completely unconnected sides but both enemies of the heroes team up to conquer a kingdom, each planning to double-cross the other, but the younger villain gets there first, thoroughly defeating the older, more experienced villain and taking over his troops. Lightning plays a significant role in both stories, as well.
- With Catlike Tread: Tuffnut's infiltration, in which he falls off his perch and lands in the middle of enemy soldiers.
- You Have Outlived Your Usefulness: Alvin and Dagur intend to do this with each other. Dagur is the one who succeeds.
- You're Insane!: Not directly to Dagur, but Savage mentions to Alvin that Dagur is known to be crazy. Alvin points out that while they're true, they need the Berserker fleet.
