It was bad enough when Jake found out his older brother was one of them. It was even worse when Tobias stayed in his morph too long. But nothing compares to the horror the Animorphs are about to face-nothing. The Animorphs have discovered the location of the Yeerks's new base. They've even figured out how to get in-and they have a plan to hit those alien slugs where it hurts. But they were never prepared for Jake to fall into a Yeerk pool. For Jake to become a human controller. The enemy. It's a race against the clock as the Animorphs face their biggest challenge yet: Save Jake before the Yeerk can expose them all!