One by one, we each stopped walking. One by one we turned to face Ax.

"Ax, are you telling us you do know what that thing is?" Tobias asked.

"Of course. I started to tell you, but we were interrupted."

"So? So what is it?" Marco demanded.

"lt's a disposable module of a type used in the old days on the first generation of Andalite Dome ships. When the modules were used up, they were jettisoned into space. They were supposed to be aimed toward a star, so they'd be burned up without a trace. This one must have .

drifted through space, eventually being caught by Earth's gravity."

"So it's a space engine?"

"lt's a weapon?"

"No, of course not. It's . . . well, this is a bit embarrassing. It's an Andalite Dome ship's modular waste disposal system."

For about a full minute, no one said anything. Then Marco spoke.

"You're telling me the Most Secret Place On Earth, the fabled Zone Ninety-one, the Holy Grail of conspiracy nuts, is hiding the secret of an Andalite toilet?"

"Only a very primitive model," Ax said condescendingly. "Since those days there have been huge technological improvements."

Chapter 21

We got out of horse morph and into bird morph and flew home.

We alone now knew the secret of Zone 91. An entire base built to analyze what they thought was an alien spaceship but was, in reality, a high-tech Andalite Porta-John.

There was, according to Ax, absolutely zero chance that the Andalite toilet would give humans the ability to fly through space.

We had done some very important things as Animorphs. We had fought some terrible and vital battles.

This wasn't one of them.

I got home just in time to walk into my living room and realize both my parents were waiting for me.

They had their angry-parent faces on.

"Where have you been?" my mother demanded.

Mom always takes the lead in discipline. She knows my dad will give in too easily. She thinks she's tougher. She thinks that because it happens to be true.

"I was out with Rachel," I said, more or less truthfully.

"Out with Rachel doing what?" my mom hissed. "You missed dinner. It's dark out. You didn't tell us where you were going."

My mom isn't a real big person. Until she's mad. Then she somehow gets larger. She seems to rise up and tower over me. It's weird. I mean, normally she's maybe two inches taller than me, but right then she was at least eight feet tall.

"We were very worried," my father said in a soft, quiet voice.

I sighed. I could feel the guilt welling up inside me. I hate it when they say they've been worried. See, I understand about worry now. I feel worry all the time for Rachel and Jake and the others. Sometimes I lie in bed at night and worry for the whole human race.

"I'm really sorry," I said.

"Where. Were. You. Young. Lady?" my mom asked, doing her one-word-at-a-time voice.

"I was just with Rachel," I said. "And Jake."

My parents exchanged a look. My dad put his hand over his mouth. He was hiding a smile. At the same time, he was trying to look extra stern.

My mom leaned back and put her hands on her hips. "You know we have discussed your dating," she said, "and I thought we decided you were still too young."

"Dating?" I said weakly.

My mom sighed. Then she shook her head. "Maybe it's time for us to have another talk about the birds and the bees."

I swear the blood drained out of my whole head. Then it came rushing back into just my cheeks and neck so that they burned. "Urn . . . I'm not dating."

"It's nothing to be ashamed of," my dad said gruffly. "You're a normal young girl, you have certain . . . interests, certain . . . fascinations, a natural . . . curiosity."

At this point I wanted to dig a hole right in the living room floor, crawl in, and pull the rug over me.

"All we're saying is be honest with us," my mom said, all stern again. "Do not make us worry about you."

"Absolutely! I swear! I will never make you worry again! Can I go now?"

I raced from the living room into the kitchen. I wanted to make myself a sandwich, carry it up to my room, and try to do at least some of my homework.

And I really did not want to be subjected to a big talk abut boys. Good grief!

I was just getting the turkey from the refrigerator when a thought occurred to me. I tiptoed back to the kitchen door and pressed my ear against it.

"See?" I heard my mother say smugly.

"You were right, as usual," my dad said.

"It's the only way. Let's face it, Cassie works so hard already, what can you do? You can't give her punishment work or make her stay in her room."

"We have a very cool kid."

That kind of gave me a warm feeling. Your parents have to love you. But I felt as if my parents liked me, too. As a person.

"Yes, we do have a cool kid," my mom agreed. "But on those rare occasions when she screws up the only way to really discipline her is to embarrass her."

They both laughed. Hah-hah-hah.

"Next time we can tell her we're going to have Jake and his parents over to discuss rules for their relationship," my mom said.

More laughter. Hee-hee-hee.

"Or as a backup plan, we could threaten to take her in to Father Banion for a family discussion about intimacy." That was my dad's suggestion.

So much for my warm inner glow. So my parents knew I liked Jake. And they knew that any discussion of that fact would embarrass me to death.

Parents. You can never completely trust them.

I finished making my sandwich and went upstairs. My room was a disaster area. I am not a neat person. I went to my desk, moved some of my junk aside to clear a work space and opened my binder to find my — Backup plan?

That's the phrase my dad had used. And Visser Three had said it, too.

Backup plan? Why would the Yeerks want a backup plan? After all, they'd penetrated the big secret of Zone 91 and it was a toilet. True, they had not understood what they'd seen, but they obviously knew whatever it was wasn't a Yeerk ship or a weapon.

So why would they still be interested?

I shook it off. Who cared now? We'd wasted enough time at Zone 91.1 had better things to worry about. Like homework. And the discovery that my parents knew more about me than I wanted them to.

I did some homework and I went to bed. At four o'clock in the morning, I woke up. I sat bolt upright and stared into the darkness.

"So it's a toilet," I cried. "That's not important. It's an alientoilet! An alien toilet! That's the point!"

Of course! Even if it was just a toilet, it meant the government had proof of life on other planets. Proof that the Yeerks did not want them to have.

The Yeerks were invading Earth. One of the reasons they were getting away with it was that no sensible person would ever believe it. Even if I went on national TV and announced that aliens were invading, who'd ever believe me? Even if I morphed right in front of people, they'd figure it was just some other kind of weirdness.

But if the government came out and said, "Look, we have proof that aliens exist," then people would start listening. People might even be prepared to believe that the Yeerks were among us.

That's why the Yeerks couldn't just forget about Zone 91. They couldn't allow the government to have any kind of proof of alien life.

There was a backup plan. That's what the visser had said.