The Secret

The ninth book in K.A. Applegate's Animorphs series, The Secret, is narrated by Cassie, one of six young people fighting a covert war against the Yeerks, a parasitic alien species whose members enter a host's brain and seize total control of the body. A person controlled this way is called a Controller. The Animorphs, five human kids and a young Andalite named Ax, were given the power to morph into any animal they touch by a dying Andalite prince. The Andalites are an alien species opposed to the Yeerk empire. Leading the Yeerk invasion of Earth is Visser Three, the only Yeerk to have captured an Andalite body, giving him the ability to morph. The Yeerks believe the Animorphs are Andalite guerrillas, not human children, and the group's survival depends on maintaining that deception.

Cassie helps her father run a Wildlife Rehabilitation Clinic and is struggling in school because her double life leaves little time for homework. She and her best friend Rachel morph into rats to troubleshoot a failing science project, violating the group's rule against morphing for personal reasons.

At a group meeting, Tobias, who is permanently trapped in red-tailed hawk form after staying in morph beyond the two-hour time limit, reports alarming news. A logging operation has appeared in the national forest where he and Ax live, guarded by armed men, shielded by a force field, and equipped with Dracon beams, powerful Yeerk energy weapons. Cassie realizes the Yeerks intend to destroy the forest to flush out the "Andalite bandits" they believe are hiding there.

Jake, the group's leader, organizes a reconnaissance mission. He, Rachel, and Tobias fly overhead as birds of prey while Cassie and Marco, another Animorph, approach in wolf morph. They find a fortified compound: a two-story log building, heavy machinery, and armed guards in tan uniforms. The guards spring a trap: Spotlights activate, steel nets drop from the trees, and Dracon beams fire from the building. Marco is pinned under a net, but Ax slices it open with his tail blade and all three escape.

Debating strategy, Cassie argues the forest matters beyond the Animorphs' safety. She proposes identifying whichever government official the Yeerks corrupted to obtain legal logging permission; protecting that person could undermine the operation without brute force. Jake agrees they need to get inside the building, and Cassie suggests infiltrating as insects.

That evening, Cassie helps her father rescue an injured skunk near the highway. The burn on its back is a perfect semicircle, the signature of a Dracon beam, making the skunk a casualty of the war. At a later meeting, Jake produces a soldier termite from the building's colony, and each Animorph acquires its DNA. Cassie is shaken by lingering fear from a previous traumatic mission morphing ants. Her father then discovers the skunk is a nursing mother with kits in the forest, too young to survive alone. Cassie secretly acquires the skunk's DNA.

At three in the morning, the group flies to the compound as great horned owls. Cassie hears mewling from a burrow during the flight and suspects the sounds are the lost skunk kits. Jake draws the Yeerks' attention in wolf morph while Cassie, Rachel, Marco, and Ax morph termites near the building, shrinking to less than a quarter inch and losing their vision entirely.

Inside the termite tunnels, the chemical commands of the termite queen override their human minds. Cassie feels her identity dissolving as instinct drags her toward the queen's chamber. Rachel's fading voice suggests destroying the queen. Cassie tricks the termite body by mentally screaming "Ant!", the termite's natural enemy, and redirects her attack instinct to kill the queen. The colony collapses into chaos. Cassie begins to demorph and nearly becomes trapped inside the wooden structure, but Ax slices the wood open with his tail blade. While Cassie recovers from a near-breakdown, Ax hacks the Yeerk computer and discovers that a government commissioner named Farrand holds the final vote on the logging authorization. Farrand is not yet a Controller; the Yeerks must persuade or forcibly infest him. Ax disables the defenses, and the group escapes.

That night, Cassie lies awake, haunted by the termite queen's death and a broader realization that all of nature rests on killing. She questions whether humans, now prey for the Yeerks, are any different.

The next morning, Tobias guides Cassie to the skunk burrow. Only four kits survive; Tobias's knowledge of the exact location implies he preyed on one. Cassie morphs the skunk mother and falls asleep curled around the kits, nearly exceeding the two-hour time limit. Jake and Marco wake her with minutes to spare. Jake, with whom Cassie shares a mutual romantic interest, is furious, berating her for risking permanent entrapment. Privately, he acknowledges her trauma but reminds her that real people depend on the Animorphs, including his brother Tom, who is a Controller. Cassie doubts whether humans deserve to survive, suggesting the Yeerks' conquest may simply be nature's course, but Jake makes the stakes personal. She asks to keep protecting the kits until the mother heals, and Jake reluctantly agrees, organizing a rotation of guard duty.

Over the following days, the group takes shifts caring for the kits. Marco names them Joey, Johnny, Marky, and C.J. after members of the Ramones, a punk rock band. The routine breaks when Ax and Marco discover Farrand is arriving at the compound within the hour, days ahead of schedule.

Cassie and Tobias track Farrand's Jeep from the air. He arrives angry, confronting the camp's leaders. Visser Three emerges in a human morph and slaps Farrand; escorts seize him for forced infestation. The Animorphs attack: Jake charges as a tiger, Rachel and Marco as wolves, Ax with his tail blade. Cassie rakes Visser Three with her osprey talons, and Tobias injures an escort. Reinforcements pour from the building, including Hork-Bajir warriors, seven-foot-tall aliens covered in natural blades who serve as Yeerk foot soldiers. A bullet strikes Cassie's wing. She crashes and wakes inside a box alongside the unconscious Farrand, trapped within the compound.

Cassie realizes the Yeerks need Farrand alive, since a corpse cannot become a Controller. She demorphs to heal, morphs into the skunk, and threatens Visser Three via thought-speak, a form of telepathic communication, warning she will kill Farrand. Visser Three orders the box opened and laughs at the small animal facing him. Cassie fires her spray directly into his face, then hits a Hork-Bajir and several Controllers in rapid succession. The stench causes total panic, and the Yeerks flee. Ax, the only true Andalite who can negotiate without exposing the group's human identities, demands Farrand's release. Visser Three, desperate to escape the stench, agrees.

Jake later spies on Farrand as a housefly. Farrand phones in his vote against logging and swears never to deal with Dapsen Lumber, the logging company, again. The group reunites the healed skunk mother with her four kits at the den.

Walking home, Cassie tells Jake she remains confused by the contradictions she has witnessed: Tobias preyed on a kit yet helped save the rest; she killed the termite queen yet attacked Visser Three without hesitation. Jake suggests that humans are unique in belonging to nature's cycle yet possessing the ability to choose to protect other species. Cassie finds partial comfort, but the contradiction remains unresolved. Tobias reports that Visser Three has been soaking in grape juice all night, still reeking, because the Yeerks mistakenly used grape juice instead of the correct remedy, tomato juice. The group laughs together, the forest and the skunks safe for now.