- Narrator: Jake
The only Kandrona source left on Earth is the Pool ship. In their desperation, the Yeerks begin the open invasion of Earth.
Tropes:
- And Then What?: Jake and Cassie discuss what they'll do when the war is over, and Cassie wheedles Jake into admitting he has no plans for the future.
- The Bus Came Back: Arbron, last seen still alive on the Taxxon homeworld in Elfangor's vision as he was taken from Earth by the Ellimist, returns to lead a Taxxon rebellion.
- The Cat Came Back: General Doubleday throws Jake in jail three times, and Jake just morphs his way out and confronts him again each time before he listens.
- Child Soldiers: The Animorphs' ages are confirmed in this book. They were thirteen when they began fighting the Yeerks, and are now sixteen.
- Cliffhanger: The book ends with Visser One cornered by the Animorphs, the Pool ship's weapons rendered inoperable by Erek, and the Yeerk in Tom about to use the Blade ship to take out the Visser and the Animorphs at the same time. The last line is Jake giving Rachel one last order.
- Disguised Hostage Gambit: To get into the Pool ship, Erek disguises himself as Cassie and allows himself to be captured by the Yeerk in Tom and delivered to Visser One. The other Animorphs are hitching a ride while morphed as Controllers and insects, and "Tom" has the Gleet BioFilter disabled so they can get through.
- Enemy Civil War:
- The Taxxons, led by Arbron, rebel against the Yeerks because they were denied the power to morph. The Taxxons only surrendered to the Yeerks because they hoped Yeerk infestation would free them from their eternal hunger, which didn't work, but morphing into another body would. The Taxxons help the Animorphs with the promise of being given new bodies when the war is over.
- The Yeerk in Tom sees a future for himself and his subordinates that doesn't require a reliance on Kandrona. The Vissers and the Council of Thirteen don't agree, which is why he goes to the Animorphs to attack his leaders so he can escape the war with an army of morph-capable Yeerks.
- Enemy Mine: The Yeerk in Tom makes a deal with Jake, allowing the Animorphs to infiltrate the Pool ship to corner Visser One.
- Even the Rats Won't Touch It: Marco reveals that the flea morph has no interest in sucking on Taxxon blood.
- Foreign-Language Tirade: Erek gives one out that doubles as a Cluster F-Bomb when Jake strong-arms him into helping the attack on the Pool ship.
- Gambit Roulette: Jake's plan to infiltrate and capture the Yeerk pool ship is a complex Batman Gambit that includes the manipulation of no less than eight separate factions,note brilliantly executed by a sixteen-year-old kid of average intelligence.
- Graceful Loser: Visser One surprisingly accepts defeat with resigned calmness, though he does insist that it was the Yeerk in Tom who did him in, not Jake or any Animorph.
- Green Aesop: Cassie's ulterior motive for suggesting anaconda morphs for all the Taxxons is to put a sentient species willing to defend a new home in the Amazon Rainforest.
- He's Back!: Played with. Jake has snapped out of his funk and is leading once more, but he's far more ruthless than he was before.
- Hellish Copter: The Yeerks allow a news helicopter to film their destruction of the city, before shooting it down when the Pool ship lands.
- Hostage Situation: Because Erek won't comply with the Animorphs' mission to take the Pool ship, Jake kidnaps Chapman and orders Erek to help with the threat of Chapman's death if he doesn't. Erek's programming prevents him from allowing Chapman's death, so he's forced into Jake's plan regardless of his wishes.
- If You're So Evil, Eat This Kitten!: Visser One refuses to buy the good stroke of luck that delivered him a captured Cassie, news of a Taxxon rebellion, and the exact movements of his enemies. So he orders the Taxxon (Tobias in morph) to eat Cassie (a hologram made by Erek), which he does. Only then do he and the Yeerk in Tom go about their merry ways to pursue their own agendas.
- Internal Reveal: Ax secret communications with the Andalite fleet are revealed to the rest, as is the Andalite High Council's plan to let Yeerks concentrate on Earth and blow it up.
- Let's You and Him Fight: Jake realizes that the Yeerk in Tom is setting up the Animorphs and Visser One to kill each other while he escapes in the Blade ship with his personal army.
- Mistreatment-Induced Betrayal: After being forced to play a part in the deaths of thousands of sentient beings, Erek backstabs Jake by draining the Pool ship's weapons entirely, leaving it a sitting duck for the Blade ship and the traitorous Yeerks on board.
- Prison Riot: Marco releases the caged hosts in the Pool ship, giving the Animorphs and the free Hork-Bajir some much-needed backup when the fighting breaks out.
- Resignations Not Accepted: After Ray is killed, some other Auxiliaries consider quitting the war. Jake refuses to let them.Jake: James, we didn’t give them morphing power so they could have fun flying around. This is when we need them. All of them. You understand? You’ve taken on the role as their leader, so lead: I want them all. Every last one.
- The Reveal: Halfway through the book, Jake gives Rachel an unknown order, admitting he has no exit plan for her once she carries it out. It's only in the third to last chapter does he tell the others that she hid in Tom's hair, meaning she's snuck into the Blade ship to take out the Yeerk in Tom by herself.
- Sacrificial Lion: Ray, one of the Auxiliary Animorphs, is killed when his leopard morph is hit by a Dracon beam. This causes the other Auxiliaries to realize how easily they could die.
- Scaled Up: Jake acquires an anaconda to show the Taxxons a morph that can go weeks without eating.
- Shape Shifter Showoff Session: Jake shows off his tiger, dragonfly, and anaconda morphs to get the Taxxons' attention while making a speech on how he can help them escape their hunger forever.
- Ship Sinking: Jake proposes to Cassie just before they go into their final mission. Cassie tearfully rejects it, saying that Jake is no longer the boy she fell in love with.
- Slave to PR: Ax reveals that the Andalite High Council is still subordinate to the Andalite Electorate, which consists of civilian politicians. This means the Animorphs can call off the Andalite fleet's attack on Earth by using the Pool ship's communications to reveal what's happening on Earth to all of the Andalite homeworld.
- Thrown Out the Airlock: Jake flushes all the Yeerks in the Pool ship's Yeerk pool into space, a total of 17,372 deaths in a few minutes, which successfully demoralizes Visser One.
- Trojan Prisoner: Erek, disguised as Cassie, is used to smuggle the Animorphs minus Rachel on board the Pool ship with Visser One none the wiser. Then "she" gets "killed" leaving the Yeerk in Tom to think he has a free getaway pass from Earth.
- We ARE Struggling Together: Earth's resistance, consisting of the Animorphs, the free Hork-Bajir, the human military, and the Chee each have problems cooperating. There's even fractures within each faction that prevents them from fighting together effectively, even with the Yeerks proving to be the biggest threat Earth has faced.
- We Are "Team Cannon Fodder": Jake sends James and the Auxiliaries on a suicide mission to attack the Pool ship with the military while the main Animorphs sneak inside with the Yeerk in Tom's help. Erek and Ax are unable to deactivate the Pool ship's weapons in time, and so Visser One takes glee in using the Dracon cannon to kill the Auxiliaries until there are none left.
- Wham Line: During the attack on the new Yeerk pool's construction site, Jake finds himself surrounded by Taxxons, facing hopeless odds. And then, one of them uses thought-speak to speak with him.Arbron: <Please do not attack, we mean you no harm.>
- Wrong Genre Savvy: General Doubleday thinks his (admittedly hard-earned) military rank is enough to make it clear he's in charge. Jake exposes three Controllers in his ranks shortly afterwards.
