The Andalite disk is still lost and the Yeerks wish to barter for it: they will trade the disk for an Andalite. Jake and Marco trick a Controller into capturing an actual animal, and think they've gotten away with the disk clean. Meanwhile, the Sharing moves forward with its plans to harvest more Controllers, and the compromise over the disk turns out to be a trap. Hopefully, the Animorphs will be able to outsmart the Controllers.
—Monica