The story revolves around five humans, Jake, Marco, Cassie, Rachel, and Tobias, and one alien, Aximili-Esgarrouth-Isthill (nicknamed Ax), who obtain the ability to transform into any animal they touch. Naming themselves "Animorphs" (a portmanteau of "animal morphers"), they use their ability to battle a secret alien infiltration of Earth by a parasitic race of aliens resembling large slugs, called Yeerks, that take humans as a host by entering and merging with their brain through the ear canal. ...