|“||While hunting for gemstones needed to complete the Dragon Eye II, Hiccup learns an old friend isn’t who he seems. Dagur faces a bully from his past.||”|
Johann, Krogan, and Viggo install the lenses in the Dragon Eye as they expect it to finally reveal the location of the "King of Dragons" but as a result none appears. Viggo sees the problem and it's that they still lack the necessary lenses. Krogan proposes to use his Dragon Flyers for a wide search effort for more lenses but Viggo has his own better plan. Johann interjects and allows Krogan to proceed with his search, while Viggo suggests they steal Hiccup's lenses. Johann agrees and already devises a way to persuade Hiccup into giving up the lenses.
Hiccup and the Riders wave goodbye to Heather, accompanied by Astrid, as she travels to Vaneheim and pays her respects to her father's grave without her brother, Dagur. Dagur reveals to Hiccup that his father possessed two dragon lenses, where Dagur used his as a toy when he was a child but lost it to someone else. When Hiccup reveals to Dagur his replica of the Dragon Eye, Dagur is set to head back to Berserker island and retrieve the lost lens. Meanwhile, Johann arrives to offer his services to Hiccup being in need of gemstones to activate Dragon Eye Two. Continuing his ruse as their ally, Johan convinces Hiccup to travel to the Northern Markets and that he brings both his Dragon Eye and lenses. Tuffnut and Ruffnut request to accompany them as well, despite Johann's objection.
Hiccup's progress in finding gemstones in the Northern Markets are hindered by the Twins' annoying obssession to acquire jewelry for their pet chicken. Johann has them sent to the far side of the market, claiming they'll find the best quality there. With the Twins' absence, Johann leads Hiccup to a narrow alley of the markets where they are suddenly cornered by Dragon Hunters on either side. Johann pretends to be unaware and in fear as the hunters threaten to kill Toothless if Hiccup dares to make a move. Hiccup gives a subtle hand signal to Toothless where he uses his tail to attack the caught-off guard hunters. Crossbowmen open fire but Hiccup deflects it with his flaming sword and Toothless fires a plasma blast to drive them off. However, when Hiccup turns around, a dragon hunter has Johann hostage and they demand Hiccup surrender the dragon eye lenses lest Johann gets killed. Hiccup prepares to surrender it, but is saved when the Twins return with Barf and Belch incapacitating the dragon hunter holding Johann. Subsequently, Toothless deals with the remaining dragon hunters. In light of the ambush, the Twins realize someone has told the Hunters in advance about their trip to the Northern Markets, but Hiccup rejects their claims of a potential mole as he believes that they just crossed paths with some hunters and seized the opportunity; they resume their search for the gemstones.
Snotlout and Fishlegs accompany Dagur to confront his former bully that he feared greatly when he was a child, Ansson the Abominable, as he currently possesses his father's dragon eye lens. But when they meet him at the harbor, they find Ansson is now known to be "Ansson the Incompetent" and is now a clumsy fisherman. Dagur now confronts his childhood bully with a smug look but Ansson replies back by greeting Dagur with the nickname he gave him, "Dagur the Dainty" despite being the Chief of Berserker island. Dagur requests Ansson to return the lens he took from Dagur but he hardly obliges. Snotlout is confused as Dagur can easily overpower Ansson and forcefully take back the lens, but Dagur promised to remain a changed individual for himself and his sister. Snotlout then suggests that Dagur propose a trade with Ansson to acquire the lens.
Hiccup obtains four of the seven gemstones needed for Dragon Eye Two and proceeds to find the others. The Twins, meanwhile, speculate as to who could fit as the mole that tipped the Dragon Hunters of their trip. However, the longer they remain in the markets, the more dragon hunters begin to trickle in in search for Hiccup. With only two gemstones left, Hiccup decides that they could find them under the empty beach of the island where the Sandbuster's lair contains large piles of valuables. Johann manages to find a built entrance for easy access underground, which makes Hiccup amazed by Johann's ingenuity. Hiccup and Johann enter alone as the Twins distract the approaching Dragon Flyers.
Dagur finds no luck in his offers to Ansson that would get him to trade for the dragon eye lens, so he asks Ansson what does he really want to finally make the trade. Ansson reveals he seeks to capture the rumored Thunderfish, to which Dagur believes is nonexistent, but Ansson is insistent he witnessed it years ago and has failed to capture it ever since, making him a laughingstock to the Beserkers. Nonetheless, Dagur agrees to help Ansson capture it as Ansson agrees to give up the lens afterwards. Ansson positions his ship at a spot in the ocean where he believes the Thunderfish is present. He drops tied items of silver and metal into the sea since the Thunderfish is attracted to shiny objects, while a doubtful Dagur watches. Almost immediately, the Thunderfish grabs hold of the dropped items and forcefully drags the ship with it. Dagur mounts Sleuther and flies overhead to get a view of the creature. Dagur realizes that Ansson is unaware that the fabled Thunderfish is actually just a Scauldron. Having enough, Dagur has Sleuther cut the ropes pulling the ship and land back. Ansson is angry that Dagur set it free but the Scauldron returns and spews boiling water on them. Dagur manages to push Ansson away from the blast but the Scauldron has them cornered and it prepares to release another blast. Ansson then bravely faces the dragon and uses the dragon eye lens to reflect a beam of sunlight towards the Scauldron's eyes which scares it away, saving a surprised Dagur.
While they traverse the Sandbuster's caves, Johann suggests to Hiccup that Toothless stand guard from a distance. Hiccup seemingly obliges as Hiccup uses a hand signal for Toothless to follow. Now alone, the pair eventually manage to find the remaining gems and when Hiccup grabs all of them, Johann makes his move as he unsheathes a dagger and demands Hiccup surrender him the lenses. Hiccup tries to reason with Johann, thinking Johann had been paid by Viggo and Krogan. Johan corrects him as he reveals that he is actually the ringleader and needs Hiccup's lens to complete his goal in finding the King of Dragons. Hiccup becomes angered as Johann releases his frustrations of having to pretend to be a harmless ally all those years but stops when he notices Hiccup lacking the surprise he expected from his revelation. Hiccup explains that he has been pretending to ignore the Twins' claims of a spy since he already knew Johann was the culprit when the dragon hunter from the ambush made him add all the pieces to the puzzle by exclaiming for Hiccup to give up the dragon eye lenses, to which he only brought with him because Johann suggested him to. Looking back in past events, Johann was pulling the strings from the very beginning: Dagur using Johann's ship during his escape from Outcast Island, lying about Dagur being unaccompanied by his fleet back when Heather planned to ambush him, luring most of the dragon riders away from their base with his distress call that allowed Viggo and Ryker to launch an invasion of the Edge, and luring Heather to a trap that caused her to give up her dragon eye lens to Krogan. But Johann reveals that he was secretly plotting their demise as far back as the events of Breakneck bog and finally has Hiccup cornered. But Hiccup reveals that the hand signal he gave to Toothless wasn't for him to leave the two alone but actually to stealthily stay close until Johann becomes a threat. Toothless lunges for Johann but is actually fooled as well when he lands on a net trap. Hiccup finally hands him over the satchel containing the lenses, but when Johann opens it, they were swapped for the Twins' chicken necklace allowing Hiccup to hide. As Hiccup tries to quietly makes his way for Toothless, he listens to Johann's rants of how his mercantile tales were just acquired accounts from real merchants he plundered and killed, and told to a gullible Stoick. Johann seemingly spots an unaware Hiccup and draws daggers at him but actually hit his reflection in a mirror. Hiccup dashes and manages to free Toothless with his sword, but an incoming dagger causes Toothless to deflect it with a plasma blast which awakens the Sandbuster. Toothless battles the wild dragon, eventually forcing it back and blocks off its entry by shooting a plasma blast at the cave's roof. During the confusion, Johann slips away and Hiccup decides not to pursue him for the time being. Hiccup and Toothless return to the surface.
Meanwhile, Dagur and Ansson return to Berserker Island with no sign of a captured Thunderfish as Dagur explains to Snotlout and Fishlegs that it turned out to be just a Scauldron. A few of the villagers present in the harbor hear this and laugh at Ansson's lack of knowledge about the dragon. Seeing Ansson about to walk away in humiliation, Dagur stands up for him and recounts Ansson's bravery against a large and feared sea dragon that he single-handedly drove away and would no longer harm the Berserkers' fishing activities while saving Dagur's life in the process. This act of bravery renders Aansson a hero and is applauded by the villagers. Dagur rejoins Fishlegs and Snotlout without the lens since he failed to honor his deal with Ansson of catching a Thunderfish. However, Ansson proves he did and hands over the lens while earning his respect by finally acknowledging him as Chief.
The next day, a returned Astrid and Heather are caught up by the revelation of Johann being the mastermind and the discovery is credited with the Twins' assistance. With the gemstones in place and with the addition of Dagur's dragon eye lens to the two they possess, Toothless lights up Dragon Eye Two and Hiccup places the three lens where incomplete markings about the King of Dragons begin to project. The Riders realize that they are now in a race to obtain all five lenses that would ultimately lead them to the King of Dragons.
- In this episode, Hiccup reveals Johann was responsible for several events in past episodes.
- Johann let Dagur escape Outcast Island with his ship without Dagur knowing and manipulated Hiccup to board The Reaper and find the Dragon Eye. ("Dragon Eye of the Beholder, Part 1")
- Johann gave Heather Dagur's locations to have her ambushed by Dagur's fleet. ("Have Dragon Will Travel")
- Johann leads the Riders away from the Edge so the Dragon Hunters could attack and get the Dragon Eye back. ("Edge of Disaster")
- Johann lured Heather into a trap so Krogan and his Flyers could take her Dragon Eye lens and sabotaged the Riders efforts to keep it safe. ("Searching for Oswald... and Chicken"/"Sins of the Past")
- Johann stated he has been working against Berk and the Riders since "Breakneck Bog", which was the episode after Johann discovered Berk tamed dragons, suggesting Johann was also responsible for other events.
- Leading the Riders to Breakneck Bog to be ambushed by Smothering Smokebreaths. ("Breakneck Bog")
- Johann told Stoick about Dagur's new weapon knowing Dagur was baiting the Riders to attack. ("The Flight Stuff")
- Johann intentionally sold Berk scrap metal he got from the Berserkers with Smothering Smokebreath eggs hidden in them. ("Smoke Gets in Your Eyes")
- Johann lured the Riders and numerous merchants to the lair of the Sandbuster to steal their treasure and eliminate the Riders. ("Sandbusted")
- Johann lured Hiccup and Astrid away from the Edge so Krogan and his Dragon Flyers could take over the Edge and retrieve the Dragon Eye from the volcano. ("Dawn of Destruction")
- Johann sent the Riders to the ship graveyard without warning them of the giant screaming eels. ("Eye of the Beholder, Part 1")
- Bringing deadly Blue Oleanders onto Berk. (Dragon Flower)
- Johann mentions Constantinople which makes sense since the Norse had contact with the city with many serving in the Varangian Guard .
- 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
- Jeff Bennett as Ansson
- David Faustino as Dagur the Deranged
- Oswald the Agreeable (mentioned)
- Night Fury
- Deadly Nadder
- Monstrous Nightmare
- Hideous Zippleback
- Triple Stryke
- Bewilderbeast (mentioned)
- Catastrophic Quaken (mentioned)
- Speed Stinger (mentioned)
- Berserker Island
- Dragon's Edge
- Northern Markets
- Outcast Island (flashback)
- Breakneck Bog (mentioned)
- Vanaheim (mentioned)
- Hiccup's Prosthetic Leg
- Toothless' Saddle and Tail Fin
- Dragon Eye
- Dragon Eye II
- Hiccup's Shield
- Johann's Daggers
- Fishlegs' Gronckle Iron Sword
- Heather's Dragon Eye Lens
- Dragon Hunter Weapons