The Hidden is the thirty-ninth book in the Animorphs series, written by K.A. Applegate. It is known to have been ghostwritten by Laura Battyanyi-Wiess. It is narrated by Cassie.

Official descriptionEdit

The Yeerks have discovered and repaired a damaged Helmacron ship. They know of its morph-seeking capabilities, and they plan to use the ship to capture the "Andalite bandits." And to find Elfangor's blue cube. The one that gave the kids the ability to morph.

Cassie, the other Animorphs, and Ax are in a pretty bad situation because they can't leave the cube in one place, they can't morph without being discovered, and they have to keep moving. It looks like this may be a battle the Visser can't lose...

Plot SummaryEdit

Animorphs 39 The Hidden inside cover only

Inside cover only featuring Cassie in buffalo morph

The Yeerks repair a downed Helmacron ship and use its sensors to track the Escafil Device and the Animorphs morphing abilities. Cassie is forced to relocate the Escafil Device. During the process, a Cape buffalo and an ant inadvertently gain the morphing ability. The buffalo morphs Chapman and begins to learn speech, and the ant morphs Cassie. Cassie kills the ant when it demorphs, and near the end of the book the buffalo is killed by a Dracon beam.


Morpher Morphs acquired Morphs used
Jake -- Seagull, Wolf, Siberian Tiger, Fly, Bottlenose Dolphin
Rachel -- Seagull, Wolf, Grizzly Bear, Fly, Bottlenose Dolphin
Cassie African Cape Buffalo (Aka) African Cape Buffalo, Wolf, Fly, Osprey, Humpback Whale
Marco -- Seagull, Wolf, Silverback Gorilla, Fly, Bottlenose Dolphin
Tobias -- Fly, Bottlenose Dolphin
Ax -- Seagull, Fly, Bottlenose Dolphin
Aka Human (Hedrick Chapman), Andalite (Alloran-Semitur-Corrass) Human (Hedrick Chapman), Andalite (Alloran-Semitur-Corrass)
Cassie-Ant Human (Cassie) Human (Cassie)
Visser Three -- Human


  • The front cover quote is, "To morph or not to morph? That is the question...."
  • The inside front cover quote is, "Where the buffalo roam..."
  • Anibase: The buffa-human is a cape buffalo that Cassie happens to end up near while on the run from the Yeerks. Somehow, it acquires the morphing power from the blue box and, while on a rampage, accidentally acquires Chapman. Suddenly, it's turning into a human. Confused, it follows the Animorphs blindly -- also confusing Cassie, who can't bring herself to destroy such an innocent creature. The Yeerks, though, have no such qualms....


International CoversEdit

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