Title: The Unknown
Description: Having learned that someone has discovered proof of alien life and hidden the proof on the top-secret base called Zone 91, Cassie and the Animorphs struggle to keep the evil Yeerks away from the place.
Subjects: Juvenile fiction, Science fiction, Metamorphosis, Extraterrestrial beings, Fiction, Children's fiction, Animorphs (fictitious characters), fiction, Extraterrestrial beings, fiction, series:Animorphs, collectionID:Animorphs