The Underground (Animorphs #17)
What's tasty, good for you, and only takes sixty seconds to make? Oatmeal. And it's making the Yeerks more than a little crazy. Now Rachel, the other Animorphs, and Ax have a new weapon against the Yeerks. Sounds good, right?
Wrong. Because it means another trip to the Yeerk pool. And the possibility of running into Visser Three. And of not being able to get back up to the surface. The Animorphs and Ax have taken chances before and been very lucky. But this time their luck may be about to run out...