Jake has made an amazing discovery: a web site about the Yeerks. Should the Animorphs investigate? If they do, they might walk right into a trap. And if they don't, they'll never know if they're fighting their enemies alone.

Rachel, the other Animorphs, and Ax have discovered a new weapon against the Yeerks--instant oatmeal--and they must make a trip down to the Yeerk pool to use it and slow down the invasion.

Cassie, one of a group of young people who has been given the power to transform into an animal in order to help fight an invasion of the alien Yeerks, decides she is tired of the battle, but she realizes she cannot quit just yet when a human-Controller named Karen learns her secret.

David, the newest Animorph, is not what he appears. His need to control the other Animorphs is all he thinks about. And the things he does are starting to break up the group. Rachel and the others know that time is running out. The newest battle against the Yeerks is the most important one yet. And it's not one that will wait. Winning this fight could mean slowing down the invasion. But no one knows what to do with David. Because the newest Animorph...

RL 5 ; 009-012. Rachael's got some pretty strange stuff happening. She can't control her morphing. What's going on? No one's sure, but Rachael and the Animorphs have to figure it out-quickly.

The blue box Elfangor used to create the Animorphs has been found by David, but David doesn't know what it is. The Animorphs have to get that box at any cost. David ends up on the run with the Animorphs and Ax, and may become the sixth Animorph.

Jake, Rachel, Cassie, Tobias, and Marco share an adventure in which their unusual abilities to transform into animals help them to solve a strange otherworldly mystery.

Cassie, one of a group of kids who have been given the power to transform into animals in order to fight an invasion of the alien Yeerks, leads her friends into yet another mission when she discovers the Yeerks are trying to access Zone 91, the most secret place on Earth.

Tobias, trapped in animal form after morphing into a hawk, agrees to help save two Hork-Bajir from the evil Yeerks in exchange for his humanity.

5. Marco has a real problem when his mother returns but not as Visser One. He has to decide whether to save Visser One from the alien Yeerks or destroy her.