My name is Marco. I've always kind of liked my name. Marco. It brings Marco Polo to mind. Not that my last name is Polo. Or maybe it is. I'm not going to tell you. None of us will tell you our last names. None of us Animorphs. Or where we live. Or anything else that would help the Yeerks find us. Yeerks? What are Yeerks? you wonder. I'll tell you. They are a species of parasites. Like tapeworms, only worse. See, Yeerks don't just crawl up inside your stomach or intestines. They crawl inside your brain. They sink their malleable bodies into the nooks and crannies of your brain. They tie straight into your brain's neurons. They control your brain. They control you more completely than it is possible for you to imagine. You think, Oh, well, I would still be able to keep control over myself. But you'd be wrong. See, if you had a Yeerk in your head right now, it would be the Yeerk that would be moving your hands and fingers; the Yeerk who'd be focusing your eyes; the Yeerk who'd be deciding if you were hungry.