Heather's locked up, despite many escape attempts, but the riders have to figure out how to retrieve the Book of Dragons from Outcast Island. Astrid decides to go undercover as Heather to retrieve it, only to find she's in over her head.
Tropes for this episode include
- Ain't Too Proud to Beg: After Astrid captures her, Heather begs to be released to go to Outcast Island to rescue her parents. She gives up the attempt when Astrid catches her in a lie about the "pirates".
- Can't Kill You, Still Need You: Astrid disguised as Heather convinces Savage and Alvin that they need her since she has the actual experience of training dragons, and the book alone won't help.
- Ceiling Cling: Heather does this in her cell to attack Bucket and escape.
- Chekhov's Lecture: When forced to tame a wild Nightmare, Astrid remembers what Snotlout telling her about Nightmares liking their horns wrestled.
- "Could Have Avoided This!" Plot: At the end of the episode, before Heather leaves with her parents, Hiccup tells her that the next time she has a problem, to just ask for help. He implies that if she had come to Berk seeking help in rescuing her parents, that he would've believed her and helped.
- Crying Wolf: Astrid finds out halfway through the episode that Heather was telling the truth about Alvin holding Heather's parents hostage. The reason why she didn't believe Heather was that the latter had lied earlier and betrayed them.
- Damsel in Distress: Astrid in the climax, when Alvin knocks her off Stormfly and carries her out of Toothless's firing range. He threatens to drop her off a cliff unless Hiccup and Toothless surrender.
- Easily Forgiven: Stormfly forgives Heather for using her to deliver the Book to Outcast Island. Astrid in turn forgives Heather for being a spy after Heather comes to rescue the riders from the Outcasts.
- Gone Horribly Wrong: Heather's spywork. She did deliver the book to Alvin, but now she's imprisoned on Berk for her role, unable to rescue her parents.
- Graceful Loser: Alvin when he sees that the Monstrous Nightmare that Astrid tamed comes back to rescue her, and the Outcasts lose the book.
- Gory Discretion Shot: One Gronckle eats an Outcast in the opening.
- The Guards Must Be Crazy: Bucket is possibly the worst guard for Heather, given she knocks him out quickly after she manages to fake an escape.
- Here We Go Again!: Alvin resorts to his previous goal to capture Hiccup, since the Book isn't enough to train them.
- Hostage for MacGuffin: Alvin tells "Heather" he'll exchange her parents for the Book of Dragons. She doesn't find out if he honors it because she tries to Take a Third Option, which fails.
- Impostor Forgot One Detail: Subverted; although "Heather" was willing to leave Outcast Island with the Book, Alvin doesn't seem surprised that she forgot about her parents being held hostage given that Savage threatened to kill her. There is also the fact that "Heather"'s eye color is different.
- Laser-Guided Karma:
- Heather used Stormfly in the previous episode to deliver the Book of Dragons to Alvin. This episode starts with an angry Astrid and Stormfly locking Heather up as she tries to escape from Berk. Heather seems to get the hint, given when she asks Stormfly for a ride she asks to find Astrid.
- Alvin sent Heather as a spy over to learn about dragon training. Astrid goes to Outcast Island disguised as Heather, to steal back the Dragon Book. In both cases, the intel missions fail right at the very end though the book changes hands in similar ways.
- Manipulative Bastard: Alvin. He threatened a teenager's parents to convince her to go to Berk and obtain dragon-training knowledge, knowing that she would take the fall if caught and would benefit him if she succeeded.
- Master of Disguise: Astrid manages to fool the twins and the Outcasts that she is Heather, despite the different eye color and face shape. Heather's parents are the only ones that notice but are smart enough to keep quiet. Alvin only catches on when he grabs her hair and the black dye smudges his fingers.
- Nice Job Breaking It, Hero: Averted. Although Astrid fails to save Heather's parents and escape with the book, and blows her cover, Alvin views Astrid's presence as an opportunity to negotiate with Hiccup and capture the riders, when before he would have killed "Heather" for outliving her usefulness.
- Not Helping Your Case: So Heather spent the previous episode spying on the riders with a cover story of how pirates destroyed her village, stole a book and a dragon from the only rider suspicious from her, and has been trying to escape from Berk's prisons. She claims that she needs to get to Outcast Island to rescue her parents, but Astrid doesn't believe her because she lied before. Lampshaded when Heather says that "I wouldn't have believed me either" after rescuing the riders.
- Oh, Crap!: Astrid when, just as she's about to leave on the Monstrous Nightmare with the Book, Alvin reveals that he's holding Heather's parents hostage and will kill them unless "Heather" surrenders the book.
- Take a Third Option: Astrid when rescuing Heather's parents tries to weaponize a wild Monstrous Nightmare so as to escape with them and the book. Alvin puts a stop to that rather quickly.
- We Can Rule Together: Alvin offers this to Hiccup and asks how it sounds.
