Marco never wanted to be an Animorph. He didn't want the ability to change into any animal he touches. And he certainly didn't want to be one of a handful of kids that are the planet's only defense against a secret alien army. His friends know why he feels the way he does. He's worried about his dad - the only family Marco has left. If anything happens to him, his father will be alone. But something big is about to change for Marco. Something that...

Warned never to stay in his animal shape for more than two hours, Tobias forgets when he becomes involved in a rescue campaign and faces being trapped in a hawk's body forever.

It all started with the dreams. But Cassie didn't pay much attention to them. She and her friends have been having nightmares ever since they acquired the power to morph. But when Cassie discovers that Tobias has been having dreams too - the exact same dreams - about the ocean, and a voice that's calling to them for help, she decides it's time to start listening. Now, she and the others have to figure out if the dreams are a message, or a trap.

Cassie believes her strange dreams are just a side effect of having been given the alien power to morph into an animal, but when she learns that Tobias has been having the same dreams about the ocean, they realize someone is issuing a call for help.

Jake and his friends take a shortcut one night and meet an alien after his ship crashes.

Rachel is still reeling from the news that the Earth is secretly under attack by parasitic aliens known as the Yeerks. And that she and her friends - five kids who, purely by chance, stumbled onto a downed spacecraft and were given the power to morph into any animal they touch - are the planet's only defense. But Rachel's always been something of a daredevil. So when it's suggested that they infiltrate the home of their assistant principal, Mr. Chapman,...

"What would you do if you were the only alien trapped on a strange planet? ... as an Andalite warrior-cadet, Ax has to be pretty cool about stuff like that. He's been hanging with the Animorphs ever since the Dome ship was destroyed by the Yeerks and his brother, Prince Elfangor, was destroyed by Visser Three..."--Cover.

We never should have done it. But we needed a break. Some time off from the superhero stuff. A chance to act like normal kids. Well - as normal as four kids who can morph into animals, a boy trapped in a hawk's body, and a bright blue alien can be. Everything should have been cool. Now Rachel is missing. And there's this... this thing that's after us. But it's not up to me to tell the whole story. Tobias, Cassie, Marco, and Ax were there, too....

When Marco runs into his old friend Erek he doesn't think too much of it. He's got more important things to do, like helping to save the world. But then Marco finds out Erek's been hanging with some of the kids at the Sharing, and he starts to think that something just a little weird is going on.So Marco, Jake, and Ax decide to morph and check old Erek out. Just to see if he's been infested with a Yeerk. The good news is that Erek's not a human-Controller....

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.