Hiccup and Toothless are doing a speed race, Fishlegs records their speed in flight with a sundial whenever they pass to a marked course. When the two finish, Fishlegs comments that Toothless is still the fastest, but that Astrid's dragon Stormfly is gaining speed fast and is almost catching up to Toothless' speed. Hiccup asks Astrid how have they've been doing it, Astrid doesn't inform Hiccup it exactly but hints she's been experimenting on what Stormfly eats, that's giving her strength and agility remarkably.
Just then Snotlout and Hookfang arrives at the Academy and informs them of his amazing discovery which he is extremely happy to have found. Snotlout leads them to the beach where they find a shipwreck ashore, Snotlout first reminds them that whatever they find inside is his property and he points what he found inside. They actually find an unconscious young girl. Hiccup wakes her up, and she gets startled.
Hiccup informs her that they're friends and intend no harm. the girl requests for a drink of water, where Fishlegs, Tuffnut and Snotlout quickly tries to give her some, to impress her, Snotlout successfully gives her the drink. Thereafter, the girl asks where she is, Hiccup informs her that she's on Berk. Toothless goes inside to take a look of her, which she gets startled, Hiccup tells Toothless to take it easy and give the girl some distance.
The stranger is utterly impressed and asks how did Hiccup do that, Snotlout tries to demonstrate it her again also to impress her too, when Snotlout commands Hookfang to come near him, Hookfang ditches his Rider, to avoid awkwardness, Snotlout informs her that he's the one who rescued her. Hiccup then introduces himself, and the girl reveals her name to be Heather.
Astrid asks Heather how'd she ended up in Berk, Heather explains that when her family was going to return to their home island, when pirates then came aboard their boat and attacked them. The pirates took them with them where they also are heading to their island, laying siege to it. Heather manages to escape but her family still lies in the hands of the pirates. Hiccup offers to let her stay with them until they figured something out to fix her situation. However, Astrid gives a brief suspicion towards her. Astrid reminds Hiccup to not forget about their meeting to work out on their dragon's speed that will determine which dragon is the fastest. Hiccup assures Astrid he'll be there, and Hiccup gives Heather a lift back to the village. Snotlout, however, has no dragon to fly back and is left alone.
At night, Stoick allows Heather to rest with their homestead, and Hiccup offers his bedroom for her to sleep in, Heather is thankful for Hiccup and his father for letting her stay, she then asks Hiccup what's with all of his sketches that impresses her, Hiccup explains those are sketches for Toothless' new gear intended to boost his speed to maintain on top behind Astrid, due to her competitiveness. Hiccup and Toothless then proceeds to sleep downstairs.
Meanwhile, Astrid is feeding Stormfly loads of chickens, which is the source where her speed strengthens, to prepare Stormfly for tomorrow. Suddenly, they hear something unusual outside and Astrid decides to check it out. A person emerges behind her, attempting to flee the scene, Astrid notices it and shocks her to identify it to be Heather, running back towards Hiccup's home.
The next morning, Hiccup is up early to work on the gear for Toothless. Heather is awake too and greets him, she then gives Hiccup advise, to forge a shorter connecting rod that'll push Toothless' saddle that'll incredibly increase their speed. Hiccup sees it as a great idea and expresses his joy that this will finally compete against Stormfly gaining the upper hand on them. Hiccup decides to test it out now, along with Heather.
Meanwhile, Astrid and Stormfly awaits Hiccup and Toothless' arrival, but to their surprise, they fly straight past them.
At the Academy, Hiccup hasn't arrive yet and the Riders are starting to get a bit cocky about Hiccup being late. Fishlegs asks where is he anyway, Astrid tells him that he's giving a 'private lesson' to Heather only. Ruffnut sees her attitude as a form of jealousy, but Astrid assures Ruffnut that she is not expressing jealousy towards Heather.
When Hiccup finally finishes their flight, Astrid expresses her disappointment that Hiccup didn't come to their meeting, Hiccup realizes it and apologizes to Astrid. Astrid then turns her attention to Heather, where she asks did she sleep well, Heather responds she did and thanks her for asking in a fake sugary-sweet voice. Astrid gives her a grim look. Heather just then moves on and watches the infrastructure of their Dragon Training Academy.
Hiccup explains to Heather that they've been training the dragons to co-exist with Berk properly and they keep track all of their training in the Book of Dragons, Heather then focuses on the book after Fishlegs shows it to her for impression, and asks if she can take a peak. Astrid suddenly interrupts and takes the book away from her. Astrid then asks to talk with Hiccup privately, leaving Heather to contend with the boys.
Astrid tells Hiccup that he shouldn't trust Heather as she doesn't trust her at all and that they should not tell her all of their dragon training experience, but Hiccup tells Astrid that he trust Heather despite her pleas meaning she should trust his judgement also. Astrid still looks on in suspicion towards Heather.
Later, Heather is asking each of the Riders, Meatlug, Tuffnut, and Snotlout, information and detail about their dragon and how they train it, the Riders accepts her requests, distracted by her innocent behavior and beauty. After that, while Hiccup is busy with Toothless outside, Heather attempts to search for the Book of Dragons inside Hiccup's room. She manages to find it under Hiccup's bed, and searches for the pages about Deadly Nadders, as she is certain that Astrid will not allow her to show how she trains a Nadder and will only raise her suspicion.
When Heather finally finds the page number, she is suddenly caught by Astrid. Moments later, Hiccup arrives in the scene and Astrid demands to explain herself. Quickly, Heather comes up of a story that she was only cleaning Hiccup's room and found the book by accident. Hiccup believes her and forgives her easily, Astrid objects after what she saw, Hiccup tells her to calm down, but Astrid replies that she's the one 'sneaking around'. Hiccup asks what she meant by that, Astrid explains her encounter with Heather last night near her home, Heather quickly explains that she only went out last night because she couldn't sleep after having terrible nightmares. Hiccup believes her story also, but Astrid is still unconvinced and cannot believe Hiccup showing forgiveness for her and she angrily leaves.
Hiccup apologize for the dispute, but Heather kindly apologizes also after reading the book without permission, but Hiccup tells him that it was nothing and he still trusts her. When Hiccup hides the book again under his bed, Heather sneakily sees it and has the opportunity again to get the book.
At night, Heather attempts to sneak up on Astrid's home where her dragon is outside, she attempts to train her first dragon, which is Stormfly, using the knowledge she read on the book of dragons, she carefully approaches it, but Stormfly sees her a threat and begins to defend herself with spines for any sudden moves. But Heather, unfrightened, speaks to herself. "Stay in the Blindspot," she says to herself. Then, she grabs chicken out of her purse and raises it to Stormily, after learning it's Stormfly's favorite. Storymfly eats it and comes toward her. After feeding her with the chicken, Stormily finally shows loyalty towards her.
Astrid arrives a little late and catches Heather, the two have a dispute. Furiously, Astrid yells at Heather and asks her what she is doing. Disappointed, Heather tells her that she likes to sneak up on people. Heather knows that Astrid is way too smart for Heather's innocent routine to be convinced otherwise. Despite that, Stormily is already showing affection towards her. Stormfly bends and goes to Heather, Heather pets Stormily and grins wickedly back at Astrid. She says that Stormfly likes her and that she will see her later.
Back at Hiccup's home, while Hiccup is busy cleaning up from dinner, Heather attempts to retrieve the Book of Dragons under the bed, but to her surprised, the book is not there and it is actually being used by Hiccup.
At the forest, Astrid is throwing her axe brutally against the trees to express her angered emotions towards Heather. She imitates Heather in a mocking voice. Suddenly, Astrid spots Heather, and instead of catching her, she quietly follows her to wherever she plans to go. Heather stands near the shore, waiting for something. Behind her, Astrid sees it as a waste of time but suddenly she spots an Outcast boat heading towards Heather.
Savage sets foot on the shore and asks Heather what she learned from the dragons, revealing Heather is working as an agent for the Outcasts. She reports her status with the dragons, but hasn't salvaged any good leads about dragon training, but she tells Savage about the Riders having the Book of Dragons that has everything about dragon training that will make Alvin very impressed. Unfortunately, Heather hasn't have it yet and promises Savage that she'll get it, but she requests she needs more time. Savage does not accept as Alvin is impatient, but she assures Savage that the wait will be worth it.
Astrid, watching the entire time, leans but causes rocks to fall raising suspicion to Heather and Savage, Heather recommends that she better leave now. Astrid races to Hiccup's home, hoping to catch Heather absence at Hiccup's room. When Astrid is about to prove and show Hiccup that Heather is outside working for the Outcasts, she is a little late, as Heather manages to sneak back to Hiccup's room and pretends that she was still sleeping.
Astrid is humiliated prompting Hiccup to be unconvinced with her claim that Heather is working for Alvin, Astrid still tries to convince Hiccup with suspicion over Heather, such as suddenly being washed up on the shore, but Hiccup still believes Heather's story that she was attacked by pirates, Astrid tells him to be more open-minded and tells him that an attack by the Outcasts is imminent. Despite her pleas, Hiccup clarifies that he claims that Heather is not working for the outcasts.
On Outcast Island, the Outcasts are struggling to control a Monstrous Nightmare, as Alvin has no clue how it just burst it's body into flames. Savage explains Alvin that they need the book to fully understand everything, Alvin asks why doesn't he have it yet, Savage reassures him that he will, but Alvin warns him that he's life depends on that.
The next day, Hiccup questions his father about the Book of Dragon's whereabouts, as he cannot find it anywhere. Suddenly, Astrid barges in and informs Hiccup that her dragon, Stormfly is gone, and claims that Heather took her and the Book also. The Riders then prepare for a search party for Heather before she arrives at Outcast Island. Hiccup is still having trouble believing Heather double cross them, Tuffnut tells him that it's because his 'Brain was under siege..', the same reason Astrid used when he was arguing with Hiccup last night. Hiccup apologizes to Astrid for being blind towards Heather, but she says to do it later after they retrieve her dragon. Astrid takes a ride with Hiccup and Toothless, and they commence the search.
Meanwhile, Heather is having trouble flying Stormfly properly causing the Riders to catch up to her, but Astrid tells Hiccup that they'll never be able to catch her on time as Stormfly is too fast, but Hiccup is confident they'll be able to. After Heather helped Toothless' speed prior, Hiccup uses it as an advantage to go near her quickly. However, Heather counters it by feeding Stormfly chicken thus boosting her speed, Hiccup discovers that's what Astrid was feeding all along but Astrid tells him to talk about it later.
The two dragons stream in blazing speed, Hiccup lets Toothless to fly above her, and Astrid jumps and lands on Stormfly. Heather and Astrid quickly results them to fight for control of Stormfly. However, they must hurry as they are nearing Outcast territory. Meanwhile, the Outcasts fire catapults upon the intruding Riders. In the last minute, Astrid finally takes Heather off of her, but causing her to fall off Stormfly along with the book.
Snotlout goes for Heather and Hiccup goes for the book, Snotlout and Hookfang manages to catch Heather, preventing her to plummet towards her death. However, Hiccup and Toothless struggle to catch the book as they are dangerously close to the line of fire, and the book is nearing land on the Outcasts. In a vain effort, Hiccup is forced to retreat as he is overwhelmed and the book continues to plummet down.
The Outcasts cheer for victory as the Book of Dragons is within the island, and Hiccup sadly reports to the Riders that he was unable to retrieve the the Book of Dragons and now it's is going to be in the hands of Alvin the Treacherous.
- Jay Baruchel as Hiccup Horrendous Haddock III
- America Ferrera as Astrid Hofferson
- Christopher Mintz-Plasse as Fishlegs Ingerman
- Julie Marcus and T.J. Miller as Ruffnut and Tuffnut Thorston
- Mark Hamill as Alvin the Treacherous
- Nolan North as Stoick the Vast
- Zack Pearlman as Snotlout Jorgenson
- Paul Rugg as Savage
- Mae Whitman as Heather
- This is the first episode to focus on Astrid.
- This episode, and the next, are slightly similar to the third book, How to Speak Dragonese, as Alvin gets Hiccup's book to learn more about Dragons and Hiccup is determined to get it back.
- This is the first episode in the first season that didn't have Hiccup's narration at the end of the episode.