Animorphs - The Unknown

It's Cassie who first notices that some strange things are going on in the Dry Lands. Horses are displaying some very unhorselike characteristics. And then there was the strange explosion that looked just like a Dracon beam...

So the Animorphs go into the Dry Lands to investigate. But they could be getting more than they bargained for. Because in the Dry Lands lies Zone 91. The Most Secret Place On Earth. A place that the Yeerks are kind of interested in, too...