This article is written from a Real World point of view.
"I decided that I had no reason to feel guilty. I had been united with the humans when we were on Earth. That made sense. But now I was back among my own people. My true place was here."

The Decision, published in April 1998 and written by K.A. Applegate, is the eighteenth book in the Animorphs series. It is the third book narrated by Ax, and the second book with Ax as the sole narrator.


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

This section needs a rewrite
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 a crowd and paramedics at the mall's Cinnabon.

They discuss this at Cassie's barn before meeting up with their friend Erek, the Chee android. Erek informs them that the second-in-command of the U.S. Secret Service, Hewlett Aldershot III, 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 Three 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 Aldershot 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, Jane Carnegie.

The Animorphs suspect that Visser Three has spotted them in seagull morph. Soon, the glass window shatters and out flies Visser Three morphed as a kafit, a six-winged bird 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. 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. Ax then suddenly has the idea that the Animorphs could morph Aldershot if they can figure out how to acquire him, with Marco adding that they could 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 rhinoceros, then the president and other government agents would have to listen to what he's saying. They aim to turn the Yeerks' plan on their head.

Animorph decision book 18 inside cover mosquito

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

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. While their excess mass is in Z-space, an Andalite ship, the Ascalin, strikes it, causing them to appear in Z-space and brought on board the Ascalin.

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 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 the City of Worms. 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 and ready to be infested, while the Animorphs decide to leave and head to the mall once again.


Featured Characters:

Supporting Characters:




Major/Highlighted Events

  • Erek King alerts the Animorphs that Hewlett Aldershot III, the second-in-command of the United States Secret Service, has been in town for some unknown reason and that Chapman ran him over with his minivan, in order to place him in a hospital under Yeerk control. The Animorphs spy on the hospital and discover that Visser Three arranged to have Aldershot injured so that he could be infested, as a way to get to Jane Carnegie, the Secret Service's first-in-command, and get her infested. However, Aldershot's injuries have seriously affected his brain stem, placing him in a coma, and thus Visser Three decides that he will acquire and morph Aldershot instead in order to get to Carnegie.
  • The Animorphs decide to acquire and morph Aldershot as well, and then use the Aldershot morph to convince Carnegie that the Yeerk threat is real. Cassie is against morphing humans while the other Animorphs find it acceptable in times of need, and Cassie suggests that they use mosquito morphs, after Ax confirms that acquiring human blood through a morph should theoretically acquire DNA. While in mosquito morph, however, their excess mass, which is floating in Z-space, is hit by the Andalite assault ship Ascalin, transporting the six Animorphs to Z-space, where they are rescued and brought on-board the Ascalin.
  • Ax is overjoyed to be with his people once more and decides not to return to Earth, and declares that Jake is no longer his prince. However, the captain of the Ascalin, Samilin-Corrath-Gahar, is revealed to be working with the Yeerk Empire and attempts to turn over the Andalites on the ship, as well as the Animorphs, to Visser Four.
  • Samelin is killed by his second-in-command, Hareli-Frodlin-Sirinial, who tells the Animorphs to morph small and escape. The Andalites on the Ascalin all commit suicide to prevent infestation, and Ax rejoins the Animorphs and places himself under Jake's command once more.
  • Ax and the Animorphs find themselves on Leera, the Leeran homeworld, where Andalite forces are struggling to prevent Leera from being overtaken by the Yeerks. Tobias mysteriously disappears, which causes Rachel to cry and become enraged, only for her to disappear soon as well. The disappearances are explained to be a snapback effect of their mass.
  • Galuit-Enilon-Esgarrouth, Commander of the Andalite forces on Leera, declares that he is a member of the highest intelligence circles and is thus aware that Ax and the humans were given morphing power by Elfangor and are causing Visser Three trouble on Earth. Galuit enlists Jake, Ax, Marco and Cassie's help, which Jake and Ax agree to. Marco, Cassie and Jake disappear, although Ax manages to succeed, giving the Andalites a major victory. Before Ax can be killed by a Hork-Bajir-Controller, he is snapped back to Earth, where no time has passed.
  • Following the battle on Leera, the Animorphs rejoice in their victory, although they leave Hewlett Aldershot III, who has been awoken from his coma, to be infested, despite the fact that their entire plan was to prevent the Yeerk Empire from having access to the Secret Service. It is this infestation that most likely led to the Secret Service Controllers featured in The Threat and The Solution.
  • The Animorphs meet other Andalites for the first time, and realize that they are not as heroic as they were led to believe.
  • It is revealed that certain Andalites are aware of the Animorphs' presence on Earth, as well as the fact that there are morph-capable humans. The adventure on Leera also causes more Andalites and a handful of Leerans to discover their secret as well.
  • Upon reuniting with his people, Ax finds himself missing his friends and Earth, and ultimately decides that humans are his people as well as Andalites, a sentiment also shared by his brother, Elfangor.


Morpher Morphs acquired Morphs used
Jake Mosquito, Leeran Seagull, Peregrine Falcon, Mosquito, Housefly, Cockroach (possibly), Brown Bat, Hammerhead Shark, Leeran
Rachel Mosquito Seagull, Bald Eagle, Mosquito, Housefly, Cockroach (possibly), Brown Bat
Tobias Mosquito Mosquito, Housefly, Brown Bat, Human (himself)
Cassie Mosquito, Leeran Seagull, Osprey, Mosquito, Flea, Housefly, Brown Bat, Hammerhead Shark, Leeran
Marco Mosquito, Leeran Seagull, Osprey, Mosquito, Cockroach (possibly), Housefly, Brown Bat, Hammerhead Shark, Leeran
Ax Mosquito, Leeran Human (Main), Seagull, Northern Harrier, Mosquito, Housefly, Brown Bat, Hammerhead Shark, Leeran
Visser Three Human (Hewlett Aldershot III; possibly) 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.
  • This is the second time that the Animorphs leave Earth, and with the exception of Ax, the first time that the Animorphs meet other Andalites as well as the first time that they are on another planet.
  • Jake, Cassie and Marco all acquire non-Earth species for the first time. Ax already had acquired and morphed Andalite animals prior to being marooned to Earth, and Tobias and Rachel had morphed Hork-Bajir in The Change.
  • 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.
  • Ax is shocked that there could be Yeerk presence on the Andalite homeworld, even though Alloran-Semitur-Corrass had told him this in The Alien.
  • This is the first and only time in the series where an Andalite (a captain of a ship, no less) is willingly allied with the Yeerks without being a Controller.


  • The kafit bird is described as having six wings, although in The Andalite Chronicles, the kafit bird was described as having 12 wings.
  • Ax worries about how Visser Three could possess a kafit bird morph, with Tobias suggesting that perhaps the kafit was in a zoo and thus not acquired on the Andalite homeworld. However, none of the Animorphs, including Ax, contemplate the fact that Visser Three's host body, Alloran-Semitur-Corrass, could have acquired the kafit prior to his infestation and therefore was a morph that Visser Three could use.
  • The Animorphs decide to acquire Hewlett Aldershot III's DNA by biting him in mosquito morph; however, this should not work since they are not acquiring him in their base forms, and the blood they receive in morph would be expelled from their system when they demorph.
  • Rachel's line on p95 is written as thought-speak as opposed to quotation marks.
  • When the Animorphs encounter Leeran-Controllers in chapter 21, the Controllers use thought-speak, even though Leerans were never said to have such a function. In subsequent chapters, Leerans and Leeran-Controllers all communicate with the Animorphs in their usual psychic fashion, making the one instance of thought-speak odd.
  • Marco's comment while acquiring a Leeran on p125 is written as if he thought-spoke, although he was in his human form at the time.
  • In chapter 23, all of Jake's lines are written in thought-speak, even though he has demorphed back to human.
  • When the Animorphs are snapped back to Earth, they discover that no time has passed at all. This would be mean that there are two versions of the Animorphs existing in the same time – one on Earth and the other traversing through Z-space, the Ascalin and eventually Leera. Based on the rules stated in The Forgotten, the Animorphs should have received flashes prior to and after the snapback of their simultaneous selves, although no such thing occurs.


US images

International Covers

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