The Decision is the eighteenth book in the Animorphs series, written by K.A. Applegate. It is narrated by Ax.

This article is written from a Real World point of view.


Official Description

Ax and the Animorphs are about to have a huge problem. It starts when they decide to morph mosquitoes in order to slip by some unsuspecting Yeerks. It ends with them stuck in Zero-space with no idea how they got there, no way to get back to Earth...and no oxygen.

Luckily, an Andalite scout ship finds them before it's too late. But now Ax is finally with his own people. And he doesn't know if he ever wants to go back to Earth...

Plot Summary

Ax is at the mall in his human morph and obsessively devours cinnamon buns after asking for a job; the manager declines because of his age but thinks he is poor. He says he can if he clears the table. Ax thinks this means eating everything he sees at the table. Marco spots Ax after he notices an ambulance at the mall.

They discuss this at Cassie's barn before meeting up with their friend Erek, the Chee android.

Erek informs them that the president's secret service agent, Hewlett Aldershot the Third, was hospitalized after being intentionally hit while crossing the street by Chapman's minivan. No one, not his family or boss, currently know where he is, and half the staff at the hospital are human-Controllers.  The Animorphs decide to go in seagull morph (except Tobias who is in his red-tailed hawk form) to investigate the hospital.

The hospital is, as expected, heavily guarded. Soon, Ax spots Visser 3 in human morph. Ax observes Visser Three demorphing to Andalite form, and concludes that he must feel very safe in the hospital to risk that demorphing. The Visser yells at a doctor that the secret service agent needs to be cured in order to be infested, because Aldershot is useless to them in his current state of being unable to move. Visser Three announces his backup plan which is to acquire Aldershot to get close to and then infest Aldershot's superior.

Animorph decision book 18 inside cover mosquito

Inside cover showing Ax morphed as a mosquito on Hewlett Aldershot's hand.

The Animorphs suspect that Visser Three has spotted them in seagull morph. Soon, the glass window implodes and out flies Visser Three morphed as a kafit bird, a six-winged birdlike creature from the Andalite homeworld. Although the kafit bird is very fast and deadly to small creatures, Ax is able to narrowly evade it through superior agility, and landing by surprise on a McDonald's arch before Visser Three can turn to catch him. Also, the Kafit bird's wingspan is too broad to fit through the arches. Ax is hit by Visser Three, and decides to demorph on the roof where humans can't see them. Ax senses fear in the Visser's eyes, as he sees the rest of the Animorphs in seagull morph coming to join Ax on the roof. The Animorphs discuss what to do next in thought-speech, and decide they don't want to fight the Visser if they can avoid it. Ax strikes once, but before he can do anything else the Visser dives off the roof. 

Visser Three lands in a dumpster and morphs to human, and the Animorphs decide to leave. For some weird reason, not only did Ax not jump in after or morph something and then jump in after him, but the other Animorphs nearby didn't land on the roof where no one else could see, morph and morph to something more powerful. It made sense not to let Visser Three see them demorph to human, but an elephant inside a dumpster on top of an Andalite? A gorilla? Think about it. It's not even clear HOW Visser Three got away when he was surrounded by humans, one of which saw him land in the dumpster, he was morphing to a more vulnerable human, presumably to blend in. But he was not at the time guarded by anyone so even more reason for the Animorphs to have Tobias follow him while the others find cover to morph into something powerful and shred him.

Animorphs decision book 18 original sketch david mattingly

The artist's original sketch for the inside cover of book 18 (showing his cat Orson).

 Later that day, Ax is running through the fields and lamenting that he let Visser Three get away.

The Animorphs regroup at Cassie's barn and discuss what they plan to do. They note that Visser Three's plan to infest or morph Hewlett Aldershot will allow him to obtain knowledge of anything the Secret Service knows. Marco then suddenly has the idea that the Animorphs could morph Aldershot if they can figure out how to acquire him, and use his morph to tell the government about the Yeerk invasion. A normal human telling the government about aliens would not be believed, but if a trusted aide could turn into a rhinosaurus, then the president and other government agents would have to listen to what he's saying. They aim to turn the Yeerk's plan on their head.

Since the Animorphs know that Visser Three will be looking out for them if they try to go after Mr. Aldershot himself, they decide to try to see if they can acquire him through blood alone. To do this, they need to morph mosquitoes.

A very rare event happens. While their bodies are in Z-space, an Andalite ship, the Ascalin, was nearly going to hit them which has never happened before. Ax and the humans became conscious that they were in Z-space and called to the ships. They were brought onboard.

The ship was headed to the home world of the Leerans. Once on the ship, Ax begins to ignore the Animorphs, instead following orders from the captain, Samilin-Corrath-Gahar. The humans are told to stay calmly in a room while the Andalites do all the work. Unfortunately, the captain of the ship reveals himself to be a traitor. He incapacitates the other Andalites on the bridge, stunning most and amputating the tail blade of the tactical officer. Ax is held, unharmed, as a hostage. Ax calls out to the Animorphs for help but they reveal to Ax that they are already present in the room. Cassie and Ax distract the captain long enough for the tactical officer to kill him. As the ship is about to be taken by the Yeerks, the tactical officer instructs them to leave while he initiates the self-destruct sequence.

The Animorphs head across the major landmass of Leera to try to find friendly Andalites. Tobias suddenly and mysteriously disappears, but the others don't know where he's gone and are forced to move on without him. Ax is struck with a sudden realization, and the Animorphs follow him out into the ocean. Rachel disappears like Tobias, and the others rescue a group of Leerans from Yeerk control. The Leerans agree to be acquired in order to help fight off the Yeerk invasion. In their new Leeran morphs, the Animorphs enter a Leeran city. The Andalites based there inform the Animorphs that they have planted a bomb to explode the continent, just as Ax had suspected, but that it needs to be activated. The Andalite scientists also theorize that the Animorphs' unexplained disappearances are the result of a "snapback" effect, meaning that when the Animorphs disappear they are reappearing either on Earth or in Z-Space. The Animorphs volunteer to activate the bomb and Marco disappears.

Soon after they set out to activate the bomb, they meet a Leeran-Controller who reads their minds and alerts the Yeerks of the bomb. When they reach the explosives, Jake disappears, leaving Ax alone. He activates the bomb but a platoon of armed Hork-Bajir appear in an attempt to disarm it. A Hork-Bajir fires at him but he disappears right before the beam hits him. The bomb goes off right after he disappears. All the Animorphs arrived back to the hospital where they were before they got sucked into Z-Space. Hewlett Aldershot III wakes up, apparently healthy again.


Featured Characters:

Supporting Characters:



Morpher Morphs acquired Morphs used
Jake Mosquito, Leeran Mosquito, Fly, Bat, Hammerhead Shark, Leeran
Rachel Mosquito Seagull, Mosquito, Fly, Bat
Cassie Mosquito, Leeran Mosquito, Fly, Bat, Hammerhead Shark, Leeran
Marco Mosquito, Leeran Seagull, Mosquito, Fly, Bat, Hammerhead Shark,Leeran
Tobias Mosquito Mosquito, Fly, Bat
Ax Mosquito, Leeran Human, Seagull, Mosquito, Fly, Bat, Hammerhead Shark, Leeran
Visser Three -- Human, Kafit bird


  • Animorphs decision book 18 flipbook

    Flipbook of Ax morphing mosquito, from the pages of the book.

    The cover quote is, "Change a little. Change a lot. Just change...."
  • The inside cover quote is, "Ax is about to bug out...."
  • This is the fourth book in which all the Animorphs acquire the same new morph.
  • The false blame that Ax takes for breaking The Law of Seerow's Kindness in order to save Elfangor's reputation to the Andalite people in The Alien is brought up in this book once more, where Ax repeats his now fabricated story to the Andalite Captain in order to explain how the Animorphs got their powers.
  • This is the first and only time in the series where an Andalite (a captain of a ship, no less) is working willingly along with the Yeerks without being a controller.


International Covers

Taken from

Main Series #1 The Invasion | #2 The Visitor | #3 The Encounter | #4 The Message | #5 The Predator | #6 The Capture | #7 The Stranger | #8 The Alien | #9 The Secret | #10 The Android | #11 The Forgotten | #12 The Reaction | #13 The Change | #14 The Unknown | #15 The Escape | #16 The Warning | #17 The Underground | #18 The Decision | #19 The Departure | #20 The Discovery | #21 The Threat | #22 The Solution | #23 The Pretender | #24 The Suspicion | #25 The Extreme | #26 The Attack | #27 The Exposed | #28 The Experiment | #29 The Sickness | #30 The Reunion | #31 The Conspiracy | #32 The Separation | #33 The Illusion | #34 The Prophecy | #35 The Proposal | #36 The Mutation | #37 The Weakness | #38 The Arrival | #39 The Hidden | #40 The Other | #41 The Familiar | #42 The Journey | #43 The Test | #44 The Unexpected | #45 The Revelation | #46 The Deception | #47 The Resistance | #48 The Return | #49 The Diversion | #50 The Ultimate | #51 The Absolute | #52 The Sacrifice | #53 The Answer | #54 The Beginning
Megamorphs The Andalite's Gift | In the Time of Dinosaurs | Elfangor's Secret | Back to Before
Chronicles The Andalite Chronicles | The Hork-Bajir Chronicles | VISSER | The Ellimist Chronicles
Alternamorphs The First Journey | The Next Passage
TV Tie-Ins Meet the Stars of Animorphs

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