The last time Rachel and her friends entered the giant Yeerk pool beneath their town things went very bad. This time they plan to be careful, and sneak in as roaches, just to spy. Once they're inside, though, the team gets caught. But right as things are looking their most dire, everything stops. Everything. Then Rachel and the Animorphs hear a voice. It belongs to a very old, very powerful being, and it says it can save them. But if it does, the Earth will be defenseless.

Ax is an Andalite, an alien, stranded on a strange planet he's sworn to defend, even though it's not his own. Since the Animorphs rescued him, he's fought at their side, and in that time they've come to consider Ax a friend. But deep inside, Ax knows he isn't their friend. He can't ever be. Andalites must always hold themselves apart, even from their allies. As the Animorphs' past actions start resulting in deaths of innocent people, however, Ax's loyalty is called into question. Now he must decide whether to reveal the reason for his estrangement - the shameful secret of his people.

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 could finally give him a reason to fight. 

There's something pretty weird going on in the woods behind Cassie's house, the place where Ax and Tobias call home. It seems the Yeerks have figured out one very important fact: Andalites cannot survive without a feeding ground. Visser Three knows the "Andalite bandits" don't feed where he does, so there can only be one other place. Now the Animorphs have to figure out a way to stop a bogus logging operation. Because if Visser Three finds Ax in the woods, nothing will stop him from finding the Animorphs.

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.

When Tobias and his friends were given the power to morph, they were also given an important warning: Never stay in a morph for more than two hours. But Tobias broke the time limit, and now he's trapped in the body of a hawk - forever. When he discovers an important Yeerk secret, Tobias knows he has to do everything in his power to destroy it. But to do so, he'll have to contend with a part of himself that's wrestling for control. A part that isn't human.

There's been an accident. Someone crash landed a Yeerk Bug fighter, and the Yeerks have been trying to cover it up - quickly. When Tobias spots it before they get the chance, the Animorphs decide to steal the ship, to show the world that Earth has been invaded. That's when things go terribly wrong. Before they know it, Jake and the other Animorphs find themselves in another place. Another time. And there's no way home....

Rachel's got some pretty strange stuff happening. She can't control her morphing. One minute, she's doing homework. The next, she's morphing a full-grown crocodile, and - without returning to human form - she becomes an elephant. That's when the floor gives way and Rachel finds herself looking up at what used to be the kitchen ceiling. What's going on? No one's sure, but Rachel and the other Animorphs have to figure it out - quickly. Because if someone sees Rachel's out-of-control morphing, the other Animorphs are in for some serious trouble.

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, who also happens to be a human host of the Yeerks, she volunteers. But what she finds inside may be more than even she can handle.

Tobias has gotten used to his new life. He's a red-tailed hawk with the mind of a kid. It was difficult when he first became trapped in his morph, but he's started to come to terms with things. After all, how many kids actually get the chance to fly? But now Tobias is about to make a very difficult choice: a choice that the other Animorphs know nothing about. And it could mean the difference between living the rest of his life as a hawk...and being human.