The Experiment is the twenty-eighth 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


The first page illustration of The Experiment

The Yeerks have decided to try a little experiment. They've decided that if they can develop a way to make people more "willing" to be infested, they can speed up Earth's invasion. So, the Yeerks try to invent a substance that will take away the human ability to make a decision. A substance that will eliminate free will.

Now the Animorphs and Ax are not only faced with trying to slow down the Yeerks' invasion, but they also have to try and put an end to the genetic testing on a small group of humans. This time there's only one chance to stop the Yeerks. And if anything goes wrong, it's all over...

Plot Summary

The Animorphs find out from Erek that the Yeerks have taken control of a meatpacking plant and a laboratory. They acquire chimpanzees and infiltrate the lab. They don't find very much information so Tobias and Ax morph into bulls (thinking they would morph into steer but not realizing that the DNA does not include surgical procedures) to go to the meatpacking plant. Inside the plant, they discover a room with humans in cages. The computer tells them that it is an experiment designed to destroy the free will of the human population so that the Yeerks can take over easily, but a Yeerk scientist eventually confirms that the experiment was a total failure.


Featured Characters:

Supporting Characters:



Morpher Morphs acquired Morphs used
Jake Chimpanzee Peregrine Falcon, Seagull, Chimpanzee, FlySiberian Tiger
Rachel Chimpanzee Bald Eagle, Seagull, Chimpanzee, FlyGrizzly Bear
Cassie Chimpanzee Osprey, Seagull, Chimpanzee, Fly, Wolf
Marco Chimpanzee Osprey, Seagull, Chimpanzee, Silverback Gorilla, Fly
Tobias Chimpanzee, Bull Chimpanzee, Bull, Human
Ax Chimpanzee, Cow, Bull Human (Main), Northern Harrier, Seagull, Chimpanzee, Great Horned Owl, Cow, Bull


  • The front cover quote is, "Change can be a good thing. A very good thing....".
  • The inside cover quote is, "Got Milk?" which is an obvious reference to a famous ad created by Goodby Silverstein & Partners.
  • The interior illustration is notably the only time in the series where one of the Animorphs (Cassie) is depicted wearing a typical form-fitting morphing outfit, rather than normal street clothes.
  • The book came with two bookmarks featuring the cover morph of Ax morphing a cow.
Animorphs 28 experiment bookmark front and back

One of the bookmarks (front and back) that comes attached in this book.

  • The regular edition came with two bookmarks of Ax morphing a cow, while the Scholastic School Market Edition contained an advertisement for the Animorphs Alliance fan club instead.
  • ANIBASE: The ending for this book made some Animorphs fans hopping mad. This is what Katherine Applegate had to say about the controversial closing scene:
"I took some grief for this from the fans. A fair number were upset that I ended with all of the Animorphs ordering hamburgers. I am in favor of being as humane as possible in dealing with livestock, but I'm not a vegetarian. I kind of think that I'll start worrying about the treatment of cows more once there are no more political prisoners, no more children dying of curable diseases, and no more fanatics blowing themselves up to murder civilians."
  • Formula 71 - The forumula that was supposed to take away every human's free will. Turns out that it's impossible to do such a thing -- but Visser Three's not listening...


International Covers

International Back 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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