The Yeerks aren't playing around anymore. They're no longer hiding behind a silent invasion. And one of the first steps in their new plan is to take over the National Guard, to prepare for all-out war against humanity.Marco and the other Animorphs couldn't be less prepared for this news. The Yeerks know who they are, forcing them to hide to protect their families. Things are falling apart, and for once Jake may not be able to make the decision that will save them...

The battle is still raging, and it's out-and-out war. Jake and the other Animorphs have found a way to slow the Yeerks down, but now the Yeerks have decided the best way to win is to just destroy everything and everyone who gets in their way.Just when things look hopeless, Jake and the others discover help where they least expected: Taxxons. Creatures so foul and heartless, it's hard to believe that they're capable of having any feelings. But Jake and the others soon discover that the Taxxon resistance has its own problems with the Yeerks. And for once, it looks like Earth may have a chance....

Abandoning all secrecy, the Yeerks load people onto underground trains that run directly into the Yeerk pool where they perform mass infestations. The vast army of Controllers is growing rapidly and will soon be unstoppable. Ax and the Animorphs can think of only one solution--to use one of the trains to blow up the Yeerk pool. But the cost may be measured in thousands of human lives.

There's a new rumor in town. Someone has discovered an item that proves life on other planets exists, and they've been hiding it on a base called Zone 91, the most secret place on Earth. Cassie and the other Animorphs already know about life on other planets. Too well. Their enemies the Yeerks will try to access Zone 91, to find out if what's there will threaten their mission to conquer to the planet. So the Animorphs decide to pay Zone 91 and the Yeerks a little visit. But what they discover is not at all what they expect.

Dak Hamee is a unique Hork-Bajir. His people call him a seer. He learns more quickly and completely than the rest of his docile race. Hork-Bajir like him are born once a generation.Aldrea is a young Andalite. Daughter of the notorious Prince Seerow. It is only after she and her family are sent to the Hork-Bajir home world that she begins to fight the Yeerks -- and, with Dak's help, ultimately discovers their hideous plan.Esplin 9466 is the Yeerk that will become the feared Visser Three. He has set out to defeat the Hork-Bajir, and begin the building of the Yeerk Empire.This story chronicles the fierce Hork-Bajir wars in a time before the Animorphs.

In a "choose your own adventure" story, the reader must decide what to do when an alien demands a mysterious blue box in return for not killing the reader's character's father.