Visser Thirty-two stood on the bank of the pool in the Yeerk zone, under his own green sky.

And on either side of him stood a creature like nothing I had ever seen or imagined. They were each about three feet tall and four and a half feet long. They were mostly a dark, dirty yellow with irregular black spots. But the head and shoulders were the deep red of the Yeerk plants.

The heads were tiny for the bodies, elongated, almost needle-sharp. The mouths were long and narrow. Hundreds of tiny, bright red teeth stuck out, jagged and wildly different in length and shape.

But what struck me as strangest was that the creatures did not have legs in the usual sense. They had wheels.

Yes, wheels. Four of them, to be exact.

The wheels were located where legs should be. Each was sloppy and irregular in shape, not perfectly round. But it was easy to see that the wheels were for real. There was mud and dirt all around them, and when I strained my stalk eyes I could even see where the creatures had left tracks in the dirt. Wheel tracks.

“Elfangor, what are those things?”

<I have no idea. I can’t imagine what evolutionary path would conceivably have created a creature with wheels.>

Visser Thirty-two actually gave a jaunty wave of his hand. <So, young Elfangor, we meet again. As you see, I brought my pets: Jarex and Larex. And you brought your pet, too. Your pet human.>

Loren looked at me. In a voice Visser Thirty-two was sure to hear, she muttered, “You know, Elfangor, I’m beginning to see why you Andalites really dislike Yeerks. Whatever body they may be in, they still have the manners of slugs.”

<Brave little human girl,> the Yeerk visser mocked. <Do you understand that even now my people are on their way to evaluate your primitive world? Do you understand that within a few years your people, you humans, will be slaves of the Yeerk Empire?>

“Blah, blah, blah,” Loren said.

I had no idea what that meant. Neither did the visser.

“You do a lot of talking for a slug,” Loren clarified. “You think I’m scared of you?”

<Yes. I know you’re scared of me.>

For a moment Loren said nothing, but her lower lip was trembling slightly. Then, she knelt quickly, plunged her hand into the water, and withdrew it. She was holding a rock. She drew her arm back, swept her arm in a big loop, and released the rock with precise timing. The rock flew through the air at an impressive speed.

And the aim wasn’t bad, either.

BONK!

<Ahhh!> the visser cried. The rock had struck him right in the face, just below his left main eye.

I don’t know who was more amazed, me or the visser.

<What … what do you call that?> I asked her.

“That? We call that softball. I pitch for Frank’s Pro Shop Twins back home. All-city two years in a row.”

<What is softball?>

“It’s a game we play.”

<And you hit people in the face with rocks?>

“Not usually.”

I was impressed by the human ability to throw things with such force. I was sure that Andalite scientists would enjoy studying humans someday. They appeared more frail and ridiculous than they were.

The visser was not impressed. He was just angry.

<So. You propel rocks at me! You’ll be very sorry you ever propelled a rock at me, human. Jarex! Larex! Attack!>

The situation stopped being amusing very quickly. The twin beasts turned their wheels, sluggishly at first. But then picked up speed.

I almost didn’t move, I was so fascinated seeing the biological wheels turn. It was truly incredible.

<You admire my pets, Andalite? They are a species called Mortrons. As a young lieutenant I went on a survey party to a world that was later destroyed when its sun went nova. We thought we might be able to make Controllers of these Mortrons, but that didn’t work out. Their brains are simply too tiny to accommodate us. Instead, I brought two of them home as pets.>

All the while the visser talked — or “blah, blah, blahed,” as Loren had said — the Mortrons gathered speed and raced around the circumference of the pool.

They made a strange sound. A HUF-HUF-HUF-HUF. Faster and faster.

<They have amazing capacities, my young friend Elfangor. As you will soon see.>

<What’s the matter, Yeerk? Afraid to fight me tail-to-tail?> I taunted. I hoped the answer was yes, because I was not at all sure which of us would win a tail fight. While I was totally confident I could deal with these Mortrons.

HUF-HUF-HUF-HUF-HUF!

The wheels spun faster, and the ungainly yellow and black monstrosities were nearly to the edge of the Yeerk portion of the pool. I watched carefully to see whether they could move from the Yeerk area into the human area.

Unfortunately, the answer was yes.

<Don’t worry,> I told Loren. <I can handle these two creatures.>

HUF-HUF-HUF-HUF-SCRINK-SHWOOOP!

Suddenly the creatures each split into two parts! The bottom portion, the yellow part with the wheels, swerved away. The dark red upper portion simply rose from the body, unfolded leathery wings I’d never even suspected, and flew straight at me!

“Elfangor!” Loren cried.

<Hah-hah! Kill, Jarex! Kill, Larex! Kill the Andalite!> Visser Thirty-two cackled gleefully.

The first Mortron — I don’t know if it was Jarex or Larex — opened its mouth and showed its rows of uneven but brutally unpleasant teeth. It powered through the air like a rocket.

I dodged left and struck with my tail blade!

FWAPP!

SPLEET! FLUMP. FLUMP.

My tail blade sliced the Mortron into two chunks. The two separate pieces fell to the ground with a wet splat.

“Elfangor, the other one!”

The second Mortron used the distraction provided by his brother to swoop wide, then arch in behind me. A tactic that would have worked on most opponents. But not on an Andalite who can see in all directions at once.

His toothy mouth was inches from my neck when I struck.

FWAPP!

SPLEET! FLUMP. FLUMP.

And the second Mortron bird-portion fell in pieces to the ground.

I was feeling pretty good, until I looked at the visser and saw the amusement in his eyes.

“Elfangor, look. Look!” Loren cried.

I turned my stalk eyes toward the ground. With amazing speed, the two bloody halves of each Mortron were growing. One piece of each was growing to become a complete bird-portion again. And the other piece was going even further — growing into a complete, two-piece, yellow and black, four-wheeled Mortron.

I had sliced both Mortrons in half. And now they were becoming four Mortrons.

<Are you doing the math in your head, Elfangor?> the visser jeered. <They regenerate! Cut an attacking Mortron in pieces and each piece grows again to become a complete Mortron. It’s the killing frenzy. It gives them an enzyme boost that makes them regenerate! Try to kill these four and you’ll have eight. Kill those eight and you’ll have sixteen! Thirty-two! Sixty-four!>

I stared in horror as the Mortron pieces grew and grew. In seconds they would be ready to attack again. And anything I did to destroy them would merely make more of them!

<Loren, I don’t know what to do. If only I had a shredder!>

“Can you outrun them?”

<Yes, I can. But you can’t! They are faster than you are. And I won’t leave you.>

“You won’t have to. Maybe. How strong is your back? Never mind, it must be strong enough. Elfangor, don’t be offended, okay?”

<Offended by what?>

“Hold still. I’m gonna try something.”

She came to me and placed one hand on the back of my neck. She placed another hand on my rump, right at the base of my tail. And suddenly, she leaned her weight on me, swung one leg up and over, and came to rest straddling my back. She sat there with one human leg hanging off either side of my back and held her hands clasped around my neck.

I turned my stalk eyes around and found myself staring directly into her small blue human eyes.

“Now let’s run,” she said.

<With you on my back?>

But even while I was standing there in blank astonishment, I saw a fully formed Mortron rise from the dirt. It was just a few feet away and it launched its bird-part. Leather wings propelled jagged razor-sharp teeth straight for my throat.

“Elfangor, this is not the time to think,” Loren yelled. “Run! Ruuuuun!”

So I did. With the human girl actually on my back, I ran.