Tobias, the other Animorphs, and Ax already have a few problems: saving the world, keeping their identities secret, finishing their homework. Now they have one more thing to add to the list. The Yeerks have discovered a way to cause a person to demorph. And with this new device Visser Three plans on capturing "the Andalite bandits." Now what? The Animorphs and Ax realize they have to get rid of the device—or be captured by the Yeerks. And the risk of getting caught is very high. That's when Tobias comes up with the only possible plan. Someone has to acquire Ax...