The Threat (Animorphs #21)

There is a new Animorph. And he's arrived just in time, because the Yeerks are preparing their biggest takeover ever. Theirultimate target: the world's most powerful leaders, all gathered together in one place. What better way to get into the minds ofhumans? Literally.At first, David joins the fight with a vengeance. But there's definitely something wrong. Because he's starting to break the rules,taking risks that could get them all captured. Or killed. The Animorphs don't know what to do. There was a time when the Yeerkswere their greatest enemy, but that's about to change...