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

"I was a human in a horse morph. I was walking along with Yeerks inside horse bodies. And we were, all of us, trying to figure out what, if anything, was being kept secret on this base."

The Unknown, published in December 1997 and written by K.A. Applegate and Michael Grant, is the fourteenth book in the Animorphs series. It is the fourth book narrated by Cassie and her third book as sole narrator.


Official Description

There's a new rumor in town. Someone has discovered an item that proves life on other planets exists. And they've been hiding it on a base called Zone 91. The Most Secret Place On Earth. Cassie, the other Animorphs, and Ax already know about life on other planets. Too well. They also realize the Yeerks will try to access Zone 91. To find out if what's there will threaten their mission. So the Animorphs decide to pay Zone 91 and the Yeerks a little visit. But what they discover is not at all what they expect...

Plot Summary

Cassie and Rachel drive with Cassie's father, Walter, to the Dry Lands outside of town. 'Crazy Helen', a client of Walter's, has informed him of a sick horse stumbling about the plains. Helen rants on about Martians while Walter and the girls search for the horse in the dark. Rachel spots it trying to make a call at a pay phone. The horse then tries to escape, but is too weak to walk, and falls over. Cassie and Rachel notice a Yeerk falling out of the dying horse's ear. Cassie, getting a bad feeling, tells Rachel to run. A second later, they're knocked over by an explosion. Cassie wakes up in Crazy Helen's caravan, who insists 'it was the Martians!'. Cassie and Rachel decide she is half right - and assume that the Yeerks were trying to keep them away from the horse.

The other Animorphs are skeptical, though. Rachel and Cassie are frustrated, but Jake allows the group to go back to the site and investigate. Cassie, Rachel, Marco, and Tobias travel in bird morph, and land in a rocky outcrop. They're promptly arrested by soldiers, and taken to the Air Force base – Zone 91. There, they meet Captain Torelli, the chief of base security, who is incredulous by the kid's lack of shoes. Cassie, Rachel and Marco, fearing being grounded, or charged with trespassing, give the captain fake names; Marco calls himself Fox Mulder, Rachel calls herself Dana Scully, and Cassie calls herself Cindy Crawford. Marco and Rachel stare at her. Marco gives them the number for the sports scores recording, Rachel gives them the number for Pizza Hut, and Cassie just gives them the numbers one-two-three-four-five-six-seven-eight. Cassie earns more stares from Marco and Rachel. The captain leaves, and the kids escape via cockroach morph. They escape outside, but Cassie is nearly crushed by a tank. Tobias picks her up, and airlifts the trio to safety.

Cassie decides on a new plan. They need horse morphs from the racetrack. They're nearly caught by the staff, and Cassie morphs Minneapolis Max – a champion stallion. The animal's jockey, assuming Cassie is the real horse, takes her to the starting gate, and she is caught up in a race, which she wins. The Animorphs are now ready to infiltrate Zone 91. Back in the Dry Lands, the teens morph their respective horse morphs.

Book 14 inside cover

Cassie in horse morph

They join the alleged Yeerk herd, and trot directly into the base. They hear the horse-Controllers speak Galard – the interstellar language. Ax translates for them, telling them that the Yeerks are planning to complete their mission tonight. The Yeerks promptly break into a run, and rush into a hangar. There, the Animorphs see what the government's been hiding. They know it's not human, but they don't know what it is. Neither do the Yeerks. The Yeerks are depressed and afraid, aware of the consequences for failure. They rendezvous with Visser Three, who decapitates the Yeerk 'responsible' for the failure. The Visser then orders his Hork-Bajir to eliminate the suspicious-looking horses standing close by. Cassie knocks over a Hork-Bajir, and the rest make a break for it. It is then that an embarrassed Ax tells them what Zone 91 have been guarding: a disposable waste module from an Andalite Dome ship - in other words, an alien toilet. The disgusted Animorphs decide they've been wasting their time, and head home.

At home, Cassie berates herself for wasting her team's time, but then realizes the significance of the Andalite toilet; it's proof that sentient life exists beyond Earth, and that Visser Three needed humanity to know as little as possible in order for the invasion to continue to run smoothly. Cassie then remembers a pin-up board for 'Gondor Industries'; the Zone 91 employees leasing The Gardens for a night out. She and the Animorphs fly out to The Gardens, where she figures that Visser Three is planning to kidnap Captain Torelli and other Air Force staff at Zone 91, in a dark and secret place. They split up; Jake, Marco, and Cassie head for the log ride while Rachel, Tobias, and Ax head for the House of Horrors. Jake, Marco, and Cassie demorph and climb down the mountain and get onto the log ride, where they encounter Captain Torelli again. The log they're all in enters a dark tunnel, Cassie steps off the log, hoping for ground, but there was no such luck and she falls into the water, where the current carries her away, and right up to the big huge drop. She falls and hits the lagoon, where Captain Torelli catches her, but he slips, which gives Cassie the chance to escape and regroup with Jake and Marco.

They soon get chased by Captain Torelli, and end up in the horror house, where Hork-Bajir and Visser Three wait. The Animorphs morph, and a battle ensues. They wound the Hork-Bajir and rescue the captain from Visser Three. The Yeerks escape in their vessels, in front of totally oblivious humans at a night parade. In the end, the Animorphs decide not to reveal the truth about what Zone 91 is really guarding and let them feel like they have a purpose.



Supporting Characters:


Other Characters:

  • Crazy Helen (First Appearance) (Only Appearance)
  • Zone 91 Soldiers (First Appearance) (Only Appearance)
  • Minneapolis Max (First Appearance) (Only Appearance)
  • Elfangor-Sirinial-Shamtul (Mentioned Only)
  • The Ellimist (Mentioned Only)
  • Tom (Mentioned Only)
  • Steve (Mentioned Only)
  • Naomi (Mentioned Only)
  • Dan (Mentioned Only)



Major/Highlighted Events

  • This marks the first time the Yeerks use and/or control non-human species on Earth.


Morpher Morphs acquired Morphs used
Jake Racehorse Seagull, Peregrine FalconRacehorse, Great Horned Owl, Siberian Tiger
Rachel Racehorse Bald Eagle, Cockroach, Seagull, RacehorseGreat Horned Owl, Grizzly Bear
Tobias Racehorse Human (himself), Racehorse
Cassie Racehorse (Minneapolis Max) Osprey, Cockroach, Seagull, Racehorse (Minneapolis Max), Great Horned Owl, Wolf
Marco Racehorse Osprey, Cockroach, Seagull, Racehorse, Great Horned Owl, Silverback Gorilla (Big Jim)
Ax Racehorse Human (Main), Northern Harrier, Racehorse, Great Horned Owl, Rattlesnake


  • The front cover quote is, "Never underestimate the power of a morph...."
  • The inside front cover is, "Born to run...."
  • This is the first book in which all six of the Animorphs acquire the same new morph.
  • Starting from The Unknown, the books were dedicated to Applegate's son, Jake, as well as her husband and co-writer, Michael. Her son was born premature in 1997, and she worked on the Animorphs series at night, in the lobby of the hospital where he was in Neonatal Intensive Care.
  • The horse on the cover is Cassie's Minneapolis Max morph, despite not fitting Max's description, as the horse on the cover is brown whereas Minneapolis Max is golden. It also does not fit the description of Cassie's original horse morph.
  • Zone 91 is an analogous reference to Area 51.
  • "Gondor Industries" is a reference to the kingdom of Gondor from Lord of the Rings.


  • Cassie states that the Yeerks have enslaved every member of the Hork-Bajir race, although both Jara Hamee and Ket Halpak were freed in the previous book, The Change.
  • Jake mentions that his father's birthday is the following night; however, in The Capture, Jake says that his father's birthday was in two months. Based on the timeline provided by the books in between, more than two months have transpired between the events of The Capture and The Unknown.
  • A tab is missing on top of p21.
  • Tobias, Cassie, Rachel and Marco fly off from the barn in their bird forms, but Cassie doesn't mention Marco being with them in them a few moments later.
  • The group lands twice on p49 and p50.
  • Another tab is missing on p67.
  • A quotation mark is missing at the end of Jake's sentence on p77.
  • On p79, Papa John's has an extra 'p'.
  • The group starts to demorph twice on p81 and p82.
  • Rachel, Cassie and Marco morph into cockroaches to escape from a military base's interrogation room, with the inhabitants of Zone 91 unaware of how they escaped and how. However, a military base, especially an interrogation room, would not only have security cameras monitoring the room but personnel observing them from outside the room.
  • A space is missing after a colon on p100.
  • When Rachel asks Ax about the Bug fighter being seen by the Air Force's radar, Ax asks what radar is. However, when Rachel asked about the Pool ship being detected by radar in The Predator, Ax knew what radar was.
  • There are six Hork-Bajir in the House of Horrors: Rachel knocks two unconscious, Tobias gouges out the eyes of another, and Ax poisoned a fourth. However, a few minutes later, all six are fleeing on foot along with Visser Three.


U.S. 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
Graphic Novels #1 The Invasion | #2 The Visitor | #3 The Encounter | #4 The Message | #5 The Predator | #6 The Capture