- Narrator: Ax
While on a mission to prevent the Yeerks from infiltrating the Secret Service, the Animorphs get pulled into outer space by an Andalite ship en route to a war on the Leeran home planet.
Tropes:
- Aborted Arc: After this book, the subplot of the Yeerk infiltration of the Andalite homeworld is dropped and forgotten about.
- Alien Sea: Leera's ocean is considered beautiful by all the characters. Ax notes that Earth's sea looks gray in comparison to Leera's blue, and Cassie talks about how some biologists she knows would cut off their limbs just to explore one small part of it.
- Ambiguous Situation: What was the deal with Captain Samilin? Why did he betray the Andalites? The Animorphs never get an answer, but his betrayal and the destruction of the Ascalin still happened nonetheless.
- Beware the Mind Reader: If even one Leeran-Controller gets away from an encounter with the Animorphs, the fact that most of them are humans will be revealed to the Yeerks.
- Brick Joke: When they're the last Animorphs on Leera, Jake tells Ax to call him "The Jake Formerly Known as Prince". When they're back on Earth, Ax does just that, much to Marco's horror.
- Broken Pedestal: This book marks the moment where Ax loses faith in the Andalite military, and begins devoting himself to the Animorphs full-time.
- Dwindling Party: Because of the snapback effect, the Animorphs have a limited time to complete their mission on Leera before they're returned to Earth. Tobias is the first to go, then Rachel, then Marco, then Cassie, then Jake, leaving Ax as the last one standing between the Yeerks and full conquest of Leera.
- Feathered Fiend: Visser Three morphs into a kafit bird, the largest bird of prey on the Andalite homeworld. Ax's seagull morph doesn't stand a chance.
- Good Thing You Can Heal: Leerans can regenerate most body parts, including the lobe on their head. Keep in mind that losing that part exposes their brain. Luckily for them, losing said lobe makes it impossible for a Yeerk to remain in them.
- Happy Place: After Samilin's betrayal and the destruction of the Ascalin, Ax imagines being back on Earth and eating a cinnamon bun.
- Honor Before Reason: When they're taken aboard the Ascalin, Ax immediately falls under the command of Captain Samilin, despite his personal feelings for his human friends. It takes the captain's betrayal for Ax to remember where his loyalties should lie.
- Impeded Communication: When they're reaching the detonation switch, Ax and Jake find their bat echolocation scrambled by the alien cave snakes who also use echolocation.
- Mind over Manners: When they morph into Leerans, Ax, Jake, Cassie, and Marco accidentally read each other's minds. After a moment of awkwardness, they figure out how to turn off the Leeran's telepathy. Ax notices afterwards that the Leeran mind feels very lonely without another mental presence.
- Normal Fish in a Tiny Pond: Despite Leera's ocean being huge (there's only one small continent), nothing that lives in it can stand up to a fourteen-foot-long great hammerhead shark. Ax speculates that the planet's geothermal energies are supporting the creatures that live in it enough that evolving into a large predator isn't necessary.
- Outside-Context Problem:
- While the Andalites knew it was possible for a ship to encounter the mass of a morpher in the infinite void of Zero Space, they assumed the mass would be destroyed if that happened. What actually happens is that the morpher snaps to awareness in their floating mass, and can be rescued by the ship, before snapping back to their original body after some time has passed.
- The Animorphs themselves to the war effort on Leera. While most of the Andalite military can morph, they actually prefer not to. As a result, the Animorphs and their wide array of morphs can be used to greater effect than Andalite foot soldiers and shredders.
- The Scapegoat: Ax once again takes the blame for breaking Seerow's Kindness and giving the morphing technology to humans, this time without any prompting. Hareli and Samilin see though his lie easily and figure out that Elfangor was the one responsible, but accept Ax breaking the law as the official story nonetheless.
- "Shaggy Dog" Story: The Animorph's plan to acquire Hewlett Aldershot through blood they steal as mosquitoes becomes moot when the man wakes up from his coma. At the same time, the Yeerks' plan to use Hewlett Aldershot and his Secret Service job to get close to America's top politicians also becomes moot, again by the fact that he woke from his coma.
- Single-Biome Planet: The Andalites and Leerans rigged Leera's sole continent to explode to prevent the Yeerks, who mostly have terrestrial host bodies, from being able to keep their foothold on the planet. When the Animorphs complete the mission, Leera presumably becomes an exclusive ocean planet.
- To Be Lawful or Good: When onboard the Ascalin, Ax chooses to be lawful and accept orders as an Andalite Aristh again. When the situation goes pear-shaped, he chooses good and returns to the Animorphs.
- The Unsmile: Ax tries to laugh at Marco's sarcastic joke, but it comes out forced and unnatural because he's not amused at all.
- The Worf Barrage: The spears used by Leeran-Controllers can easily kill other Leerans, but a hammerhead shark can shrug them off.
- You Are a Credit to Your Race: War Prince Galuit initially dismisses the humans and speaks to Ax only, until Ax directs his orders to Jake. After a conversation with Jake, Galuit privately tells Ax <I've known worse Princes than this one.>
