During their search for the villainous Dagur the Deranged, who has escaped from prison, Hiccup, Toothless and the Dragon Riders discover a mysterious object, which contains not just secrets … but their destiny. 
- Dagur the Deranged, along with his followers, escape Outcast Island.
- Hiccup discovers the Dragon Eye, which is soon taken by Dagur.
Three years after the war with the Berserkers ended, Dagur and the Berserkers, along with some still rogue Outcast soldiers are all held in prison in Outcast Island for their crimes and injustices. Dagur, who is now a buff and brutal man, knocks out an Outcast prisoner, who is jealous for Dagur's food, near his cell after being tired of his annoying voice. In reality, the food that the prison guard gave him is actually a heavy cloth where the key to his cell is wrapped in it. Dagur breaks free and fights his way against several prison guards, when he nears the exit, one prison guard is all alone and surrenders to Dagur in fear, but pleads to not hurt him as he reveals he is the one who gave the key to his cell in the first place. Dagur points him as a traitor to Berk, but despite this, Dagur carelessly still knocks him out. When he prepares to escape the Island by the ships parked on the harbor, Dagur declares to himself that he is coming for Hiccup with absolute revenge.
Hiccup and Toothless are flying throughout Berk, as the other Riders have moved on after the battle with the Berserkers ended. Snotlout now works for Gobber as a 'test subject' to see if the new weapons and defenses are a success. Ruffnut and Tuffnut Thorston have dedicated their lives to Loki "the God of Pranks", by that they are now known for causing impressive pranks throughout the village. Fishlegs is now a somewhat Dragon Historian in Berk showing and teaching the children of Berk the history of the Dragons. Hiccup and Toothless are still venturing out on the archipelago, relentless for their search of new dragons, just as Astrid and Stormfly catches up with them. Astrid wants to tell Hiccup something, but Hiccup is so caught up by his search as he claims to have finally spotted a new dragon on a sea stack and flies to check it out. In truth, the Twins have pranked Hiccup, and Hiccup and Toothless leaves dissapointed. Later on, Hiccup and Toothless rests on a sea stack, where Astrid tells him to admit that maybe their search for new adventure is over as they've visited every island on the archipelago. Hiccup still refuses to accept this, but Astrid says otherwise, saying it's over for her as she reveals that she has now joined the Berk Guard. Hiccup is sadly happy for Astrid's decision and the rest of the Riders to have found a new hobby, Astrid leaves saying to Hiccup to think about finding something else that is best for him and Toothless.
At night, Hiccup visits the old Academy, where he is the only member left to not have retired and faces the fact that it's just him and Toothless from now on. The next day, Mulch and Bucket are pranked by the Twins by pretending they are the sea monster, however, the Twins unintentionally save Trader Johann's life from drowning into the ocean as he is now at rest on Barf's neck. Meanwhile, Hiccup, having nothing else to do left, is trying to have a father-and-son talk with Stoick, but Stoick asks Hiccup what's the problem. Hiccup admits that he needs to finally 'move on' and find a 'new life' but before he and possibly be like the other Riders also, but before he can finish, the Twins interrupt with an exhausted Johann, revealing that Dagur has escaped prison and is now quickly assembling a plan to get revenge on Hiccup.
Hiccup and the other Riders gather at the Academy as they have to figure out where Dagur has left after stealing Johann's ship and throwing him overboard. Snotlout complains that they have to search everywhere to find him, luckily Johann finally awakens after fainting, and reveals that Dagur has probably set out to a fog bank just outside the outer group of islands in the Archipelago as Dagur possesses Johann's important map that points to there. The fog bank is housed by a graveyard of ships where Johann confesses it's where he hides all of his treasure, he warns the Riders of one ship that they must avoid at all cost, called The Reaper. Johann once set foot in it and discovered that every inch or yard on deck is armed with deadly booby traps; he barely made it out and promised himself to never re-enter the ship again. Hiccup and Toothless prepares to venture alone, but asks if the Riders can join him if they have time to skip their busy schedules for the day.
Finally, after three years, Hiccup is in joy to see that all of the Riders are now going to another mission as Hiccup names it to be 'the old days'. Hours later at night, Hiccup and the Riders arrive at the graveyard and witnesses unfamiliar and strange heavily damaged ships. The Riders split up in the graveyard for any sign of Dagur's arrival. Hiccup finds the ship Johann has warned about, The Reaper as he searches through the graveyard. A while later, the Riders gather at a ship and report that Dagur hasn't arrived yet, Hiccup plans on waiting for him, but Astrid and Fishlegs proposes that they return and come back later, but Hiccup tells them they can't as Dagur might already steal all of Johann's treasure while they're gone and used it to assemble and rebuild an army. The Twins propose that they 'steal' the treasure first, Hiccup sees it as a good idea and tells them to gather as much of Johann's treasure as possible but be aware of Dagur's presence. Suddenly, Giant Screaming Eels attack the Riders, causing most of their dragons to flee in fear leaving the Riders unable to escape. Toothless is the only dragon left unafraid to fight back, he and Hiccup tries to fend off the eels, as the eels begin pulling the ship into the ocean. The Riders hold on for dear life, however Astrid is unable to cling on to the Riders for much longer and she falls to the ocean. Just as the eels are about to attack her, Hiccup and Toothless dive in and fight them off, rescuing Astrid. The eels flee, and the ship resurfaces. Snotlout complains that Johann could've warned them about the giant eels. Hiccup tells him to relax and to just go forward with the plan, Hiccup then decides to see what's inside The Reaper that anyone would booby trap the ship.
As Hiccup and Toothless lands on the ship: almost immediately, a booby trap is activated that almost drags Hiccup overboard with an anchor, but luckily Toothless rescues him. Meanwhile, the Riders are now scavenging Johann's treasure where they are in joy to see such valuable riches aboard on the ships. Hiccup and Toothless goes down below and find cages made from large, sturdy straps of metal, with the remains of old dragon bones within them. This upsets Toothless as he witnesses the tragedy, Hiccup plans to go back instead, but he activates another booby trap causing them to flee deeper into the ship. They find a door that leads to the Commander's headquarters, Toothless breaks it open with a plasma blast. Hiccup finds inside to be a strange and unfamiliar artifact, Hiccup believes it to be important and decides to take it for himself and not for Dagur. However, upon claiming it, he activates a lot of booby traps and runs for the exit with their lives on the line.
Fortunately, they made it back on the ship's surface but only to be held at arrowpoint by Dagur and his fellow Berserkers where they have imprisoned the other Riders in the cages on the Reaper. Dagur demands the Riders to give up the gathered treasure, such as the jewels inside Ruffnut's mouth and also the artifact Hiccup is possessing. Once they surrender it to Dagur, Dagur says farewell as he begins to escape and prepares to assemble his new army. As Dagur begins to leave, the Riders tell Hiccup to forget about them and go after Dagur. But Dagur was expecting this and fires a catapult, Hiccup thinks his 'brother' missed, but Dagur tells him he 'never misses'. To Hiccup's surprise the fired boulder was aimed at The Reaper creating a hole that begins to sink the ship into sea.
Now, Hiccup must decide with a tough choice again whether to save the still-trapped Riders on the quickly sinking ship or to stop Dagur from escaping.
- The Dragon Hangar is under construction.
- The armor on the Reaper is the same as Alvin the Treacherous's.
- Two of the Outcasts mention a "woolly igloo" before Dagur knocked them out. This is a reference to "A View to a Skrill, Part 2", when Tuffnut is telling jokes to a small group of Outcasts.
- Fishlegs mentions the Speed Stinger attack from "Frozen".
- Snotlout mentions the riders exploration to Breakneck Bog, from the episode "Breakneck Bog".
- The Reaper's sail is the same design as the ship's on Icestorm Island in School of Dragons. In one quest, the Archaeologist wonders if it belonged to the ancient tribe from the island or another.
- Snotlout mispronounces Johann's name at one point.
- The Dragon Eye already has a Snow Wraith tooth in it when Hiccup finds it. In the next episode, it's gone.
- The hair that Snotlout finds has the same braiding as Ruffnut's when she cut it in "Free Scauldy".
- So far, this episode and the next are the only two-part episodes that do not have Heather in them until The Wings of War.
- This is the first episode of the Netflix Original series Dragons:Race to the Edge.
- The Netflix overview lists the episode as "Eye of the Beholder, Part 1."
- Jay Baruchel as Hiccup Horrendous Haddock III
- America Ferrera as Astrid Hofferson
- Nolan North as Stoick the Vast
- Chris Edgerly as Gobber the Belch
- Christopher Mintz-Plasse as Fishlegs Ingerman
- Andree Vermeulen as Ruffnut Thorston
- T.J. Miller as Tuffnut Thorston
- Zack Pearlman as Snotlout Jorgenson
- David Faustino as Dagur the Deranged
- Michael Goldstrom as Trader Johann
- Thomas F. Wilson as Bucket
- Tom Kenny as Mulch