The episode opens in Outcast Island, in the dragon cages, where all the wild dragons of the island are locked up. Hiccup is shown all the dragons that the Outcasts have captured by Alvin the Treacherous, though Hiccup desperately wants to see Toothless, and Alvin tells him that he'll see him soon enough. Hiccup admits that Alvin's plan was really not bad, except for the part where Mildew is turned into an Outcast and using him against them.Hiccup is first shown a wild Whispering Death in one of the cages. He observes how poorly the Outcasts were handling the dragon, and he tells Alvin that the Whispering Death will keep on erupting and diving back to its hole. Secondly, Hiccup is shown a Scauldron, which sucks water and shoots boiling water at one of the Outcasts. Hiccup remarks that a Scauldron was impressive, but they might want to cut down its water supply. Next, Hiccup is shown to a cage which seemed empty, and one of the Outcasts exclaim that it has escaped again. Hiccup replies that actually, it is right behind them- the Changewing. The Changewing reveals itself and shoots acid at the Outcasts. Hiccup remarks that they really don't have a handle on these dragons. Alvin replies to him that was the reason he (Hiccup) is here, and welcomes him to his new job. Hiccup replies that he couldn't take up the job, to which Alvin replies why he has to make things difficult for himself. Hiccup in turn replies that it was really not the first time he has been asked that question. He is then taken to the cage where Toothless was locked up. The Outcasts have tied up Toothless very tightly, so that he could barely move. Hiccup gets so upset seeing Toothless in this state, and tells him that he will get him out. Alvin says that Toothless wasn't going anywhere, and neither was he. Hiccup should help him train those dragons. He is then taken to his own cage, and Savage teases him saying if he could get him anything- food, a cozy blanket or some yak milk.
Meanwhile, the riders have arrived at the Isle of Night. Fishlegs is excited to see Night Furies in their natural habitat. Stoick tells the teens to search the south side of the island while he and Gobber check the north. Astrid reminds them that it should be crawling with Night Furies and tells them to fly low until they get a sense of where Hiccup might be, and how many Night Furies there are.
Back in the Outcast prison, Hiccup is trying to pick the lock with a stick until he hears someone coming. Alvin and Savage have arrived, with Mildew. He tells Alvin he gave with what he wanted, and they had a deal. Alvin says he didn't like that deal, so he changed it. He throws Mildew in a cell and takes Fungus. He them tells Mildew his final meal is lamb. Mildew is on the verge of breaking down as he watches his pet being taken away, regretting what he has done.
The teens continue their search when Astrid, Fishlegs, and Snotlout discover a Night Fury. However, once they get closer, they realize it's not a real Night Fury, but the fake one the Outcasts used. Just then, the twins show up and blast the decoy, believing it to be a real one. Astrid snaps at them, saying if that was Toothless they could have killed him. Stoick and Gobber arrive on Thornado, saying they saw Barf and Belch fire from the sky, Astrid tells them they found a fake Night Fury, but the twins blew it up. Gobber examines one of the remains and the hide was made from dragon skin and covered with ash from a charred Loki tree. Snotlout says he never heard of it when Stoick and Gobber tells them it only grows in one place: Outcast Island. They all realize this was a trap and that Hiccup is on Outcast Island.
Hiccup is now trying to burrow his way out with a rock, only for Mildew to tell him it's hard to watch. He then tells Hiccup he needs to get to his dragon. When Hiccup asks him how to do that, Mildew replies "by giving Alvin what he wants."
In the dragon pit, the Outcasts have taken up on Hiccup's advise about the dragons. The floor for the Whispering Death has been reinforced with cast iron and the Scauldron only gets enough water to keep it alive. Alvin is impressed, saying Hiccup have proved himself already. Savage suggests to Alvin he'd be quite a sight riding on the Night Fury. Alvin agrees, and says he'll have to change his name to something worse than "the Treacherous." However, he notices something is wrong with Toothless. The guard tells him the dragon won't eat or drink, and he hasn't moved in hours. Alvin tells him to keep him alive, knowing if Toothless dies he loses his leverage with Hiccup.
Back in the cell, Hiccup calls the guard over, and he'll tell Alvin whatever he wants to know. As the guard is unlocking the cell, Hiccup has taken off his prosthetic leg. Once the door is open, Hiccup whacks the guard with his leg. However, he's still conscious, as Hiccup said his plan worked a little better in his mind. But to his surprise, Mildew uses his staff to knock the guard against his cell, knocking him out. Hiccup grabs the key and starts to leave when Mildew ask him to take him too. Hiccup is reluctant at first, but Mildew says he knows how to get around the island and wants to make it up to Hiccup. Seeing he has no choice, Hiccup unlocks Mildew's cell and tells him not make him regret it. The two them make their escape.
Meanwhile, two Outcasts are trying to feed Toothless a fish, but he is still unresponsive. They then take off the muzzle, to try to get him to eat. Once the muzzle is off, however, Toothless immediately blasts the guards and bites his way out off the restraints. He gives the two a warning roar to let him pass, which they obey. Toothless then whacks them with his tail on the way out.
Hiccup and Mildew get out of the prison, where Mildew replies the quickest was to get to Toothless is through a field of wild dragons. Hiccup calmly tells them to go, but Mildew is hesitant. Hiccup tells him to stay behind him, but he's not too thrilled having a 90 pound boy as his human shield.
Toothless begins to make his way across the island by following Hiccup's scent. He is then boxed in by two groups of Outcasts, but easily blasts them away and continues his search.
Hiccup and Mildew continue to make their way passed the dragons, who notice them but only stare. Then an orange and dark green Deadly Nadder confronts them. Mildew tries to defend himself with his staff, but Hiccup stops him, as the last thing they want to do is threaten the dragon. Hiccup slowly makes his way toward the Nadder's tail and gently pets him, calming him down. Mildew is impressed by this, but the dragon then decides to check out Mildew. Hiccup tells him to be relaxed, which is not easy for the old man, but the Nadder appears to have taken a liking to him. Hiccup then says they'll need a way to get passed the guards at the dragon pit, and how they just found one. The Nadder then gives Mildew a big, sloppy lick.
With the Vikings, Astrid asks about the plan to save Hiccup and Toothless. Stoick tells them that Alvin will expect them from the sky, so they need another way on to the island. Gobber notices a ship and the gang checks it out.
Toothless has finally found his way to to the Outcast prison, where he notices Hiccup and Mildew's footprints, but they are not there. The guard finally comes to when he sees Toothless. He locks himself in one of the cells to protect himself. Seeing how Hiccup is not there, Toothless leaves to find his rider.
At the docks, Trader Johann has arrived, and the Outcasts are happy to see what he's got. Johann tells tells them he's got all kinds of weapons, and a little something special for his friend Alvin. He opens the hatch and Stoick, Gobber, and the teens run out and quickly defeat the Outcasts. Stoick grabs one and demands to know where his son and his dragon are.
Back with Hiccup, he gives Mildew a crash course on dragon training, telling him it begins and ends with trust. Mildew appears to have got the hang of it, until Hiccup tells him to get on the Nadder. Once they're on, Hiccup remarks "Mildew on a dragon. This is going to take some getting used to." The Nadder is a bit anxious, as he's never had people on him before. Hiccup tells Mildew to spit in his hand and rub the dragon to sooth him, which it does. They then take off. Mildew immediately grabs on to Hiccup out of fear. Hiccup awkwardly tells Mildew that he can grab on to the dragon, but he nervously replies he's fine. Just as they take off, however, they miss Toothless who desperately calls for Hiccup.
Once Hiccup and Mildew reach the dragon pit, they see that Toothless is gone. Just then, the cages holding the Scauldron and Changewing open out. Alvin, who is at a safe height, releases them, along with the Whispering Death, to test Hiccup on what he can do with some real wild dragons. Hiccup then tells Mildew to do exactly what he says. Initially reluctant to listen, Mildew replies he's all ears. The two get back on the Deadly Nadder and try to avoid the dragons' attacks. The Whispering Death then begins to dig, and Mildew expresses relief at the dragons apparent departure. Hiccup then tells him otherwise that "Changewings shoot acid, Scauldrons fire boiling water, and Whispering Deaths hunt from UNDERGROUND!" Hiccup then tricks the three wild dragons into colliding with one another and they make their escape, much to Alvin's displeasure.
When they reach the outside, Mildew comments that Hiccup really knows his dragons. At that moment, Stoick, who is glad his son is alright, and the others show up. Tuffnut finds it weird that Mildew is on the back of a dragon, just as Gobber pulls him off, threatening to run Mildew through for betraying his tribe and turning Hiccup and Toothless over to the Outcasts. Hiccup stops him and tells the other he helped him escape, much to everyone's surprise and confusion. Hiccup then tells them he has to get to Toothless, when Astrid reminds him he can bring the dragon to him. Hiccup then sends out his Night Fury call across the island, Toothless, who is trying to find Hiccup's scent, recognizes the call and responds. He then runs toward the sound, as the riders get back on their dragons and follow the call. Hiccup spots Toothless in a ravine and lands. Once he and the others dismount, Hiccup runs toward his friend and Toothless tackles him to the ground out of happiness. The two friends are finally reunited.
Just then, Alvin shows up, wanting to finish his business with Hiccup, even by going so far by calling him "Stoick's little runt." Hiccup, who has grown angry with Alvin's antagonism towards himself and his friends, gets on Toothless and takes off toward the Outcast leader with lethal intent, despite his father's objections as Alvin defiantly mocks and goads him. Once they get close enough, Alvin signals the Outcasts and they launch another bola around Hiccup and Toothless, restraining them both. Once again captured, Astrid tell everyone to get to their dragons, but they are gone. To everyone's amazement, the dragons, including the recently trained Nadder, have already gone to save Hiccup and Toothless. The Nadder and Thornado are the diversion, Barf and Belch and Meatlug create fire walls to keep the Outcasts at bay, and Hookfang and Stormfly pull Hiccup and Toothless to safety. Hiccup is just as surprised by this rescue, and Astrid says the dragons have taken their training to a whole new level. Stoick then reminds everyone they need to leave, so they all get back on their dragons and make their escape. Gobber and Mildew are on the Deadly Nadder when Mildew ends up hanging by the tip of its tail. Gobber tries to tell the old man to hang on, but Mildew, who tells Gobber to let Hiccup know he's sorry, let's go, seemingly sacrificing himself to buy them time to make thier escape. Hiccup tries to go back for him but Mildew warns Hiccup to leave him. Stoick tells his son that they can't help him now that he has been recaptured. Hiccup turns around and the Hooligans head back to Berk. Mildew is taken to Alvin, where it is revealed that he was STILL working with the Outcasts. It was all a trick so Mildew could about training dragons from Hiccup. Even Fungus is okay. Alvin then states "tomorrow is a new day for the Outcasts."
Back on Berk, Hiccup throws the fake map into the fire and apologizes to Toothless for it not being the real thing. But he adds there was nothing wrong with being one of a kind. Astrid arrives, reminding Hiccup about the parade for Bork Week. He and the other riders take off, with a closing narration:
A family isn't just something you're born into. It's also the friends who stood with you. The ones who fought by your side. You know you'll be there for them, and they'll be there for you. For the battles that are yet to come.
At the Outcast kill ring, Alvin attempts to train the Whispering Death... and succeeds. He, Mildew and an Outcast let out an evil laugh (Mildew coughs on his) as he has finally achieved his goal...
- Jay Baruchel as Hiccup Horrendous Haddock III
- America Ferrera as Astrid Hofferson
- Christopher Mintz-Plasse as Fishlegs Ingerman
- T.J. Miller as Tuffnut
- Brook Chalmers as Outcast Gusrd/Outcast Soilder
- Chris Edgerly as Gobber the Belch
- Michael Goldstrom as Trader Johann
- Mark Hamill as Alvin the Treacherous
- Julie Marcus as Ruffnut
- Nolan North as Stoick the Vast
- Zack Pearlman as Snotlout Jorgenson
- Stephen Root as Mildew
- Paul Pugg as Savage
- The Scauldron in this episode is a lot smaller than the one in Dragon Flower, indicating that it might be a juvenile.
- Trader Johann makes his third appearance in this episode. In episode 9, he welcomes the Vikings and says,"Ah, Berk! My favorite of all the islands I've traveled to!" When he reaches Outcast island, he says,"Ah, Outcast Island! My favorite of all the islands I've traveled to!" This may indicate that Trader Johann says the same thing in all islands, or maybe he says this as a part of the plan of the Vikings to trap the Outcasts.
- Mildew agrees to ride on a dragon for the first time- a Deadly Nadder.
- Alvin finally achieves his goal and trains a dragon for the first time- a Whispering Death after Hiccup's closing narration.
- Alvin is the first Outcast to train a dragon.
- When Hiccup is first locked up his handcuffs are still on. In the next scene, however, they're gone.
- It's night when Hiccup and Mildew want to save Toothless and go into a cave but when they come out minutes later, it's broad daylight.
- This is the second episode in the first season that didn't have Hiccup's narration at the beginning of the episode first being Heather Report Part II.
- When Alvin's Outcasts go to Trader Johann's boat, one pushes an Outcast doing a Wilhelm scream.