"Battle of Bunker Hill? No oatmeal used by the British, no oatmeal used by the Americans," Jake went on. "D-Day? No mention of oatmeal."

"Okay, I'm ready," Tobias said.

"Let's do it, and then let's get out of this place," I said.

I focused my mind on the bat. The bat DNA had come from a common brown bat. Not a very big animal. More like a mouse with wings.

It was a strange sensation. I was shrinking. Probably. But I couldn't see anything. So I couldn't see myself getting smaller. Couldn't see any of the changes.

In the absolute darkness I was left with just my sense of hearing. I heard things I seldom noticed. I heard my thick, human bones grinding and suddenly squishing as they went liquid. I heard a sound like my stomach rumbling from hunger. Only it was the sound of my stomach and all my internal organs shifting and moving. Some organs shrank. Some basically disappeared. All of it was happening inside me at a point when I didn't even know if I was five feet tall or five inches.

I reached with my hands to touch my face and "see" how much I'd morphed.

But my hands were restricted. They were weirdly jointed. And when I moved them I heard a faint sound like leather being folded.

I flapped my arms. Yes, I had wings. The paper-thin leather of bat wings.

And then, I felt that most vital of bat powers: I felt the echolocation.

I fired an ultrasonic blast. Sound waves pitched higher than any human ear would ever hear. But I heard them. They came bouncing back to me and I heard every distorted, twisted, shattered echo.

"Oh!" I said in amazement. I'd been a bat only once before, and only for a short time. I'd forgotten the stunning array of information that comes from echolocating.

It was as if I'd been blind and allowed to see.

Not "see" the way humans see. But to see shapes, edges, openness, and narrowness. I fired another burst and I "saw" the edges of a thousand bats clustered above us. I saw their tiny, doglike faces and their big feathery ears as they hung down with wings folded demurely.

It was as if all the world were drawn with pen and ink. Edges and outlines, no hint of color. And each picture was only a flash, only there as long as the echoes lasted.

Now the others all began echolocating, and I redoubled my own efforts.

Yes! I could see the cave. A comic book drawing of a cave, thin lines and thick ones.

I flapped my wings and lifted off heavily, rising from the floor of the cave. I took a quick turn around, absolutely confident of where I was flying.

"It's not quite like seeing, but it beats being blind," Cassie said, sighing with relief.

I realized the others had been as stressed as I was by the utter darkness.

"To the Batmobile, Robin," Marco said.

"How about if we just get out of this place?" Tobias suggested.

"I'm with that," Jake said.

We flew. Through the cave, which wound and twisted, always beneath hanging bat stalactites, and above a carpet of bat-guano stalagmites.

I could feel the way out. I could feel the slight changes of air pressure, the changes of temperature that showed the way out. But then . . .

"You guys feel that?" I asked.

"It's coming from our left," Ax said. "My echolocation is showing an opening. But not an opening to the outside."

"Oh, man," I moaned. I could feel the near- ness of the cave opening. But I could also feel this other exit. I had a pretty good sense of where that second exit might lead.

"We could just go home," Jake said. He was offering us all a way out. Go home, forget about it for now. He didn't want to "order" us to go on if we weren't up for it.

Everyone in a group has a role to play. At least that's how it always works out. My role was to say, "Let's do it. Let's go. That's what we came here for."

But I was tired. And I'd had a really, really bad few days digging down to this stupid cave.

So I said, "Let's do it. That's what we came here for." Sometimes it's hard to get out of a role once you've started playing the part.

It was a vertical crack in solid rock. In places it was no more than eight inches wide. At its best it was a foot wide.

With wing tips scraping the rock wall, we flew. Through a world seen only in echolocating sketches, we flew.

"Cool! This is so Star Wars!" I said, genuinely enjoying it. "Remember when they're attacking the Death Star and -"

Suddenly, the crack plunged downward. Down ten feet and then -

"Whoa ho!"

We blew out into a world of light! I could see again. People think bats are. blind, but they're not. I could see a vast, open area lit with stadium lights down below us.

We fluttered in a circle at the top of a dome. The crack we'd entered through was high up, almost at the very peak of the dome. And down below us was the Yeerk pool.

"Well," Jake said, "we found our way into the Yeerk pool."

"Yeah. Great," Cassie said darkly. "Now what?"

"Now we figure out how to get that oatmeal in here and feed it to a bunch of human-Controllers," Tobias said.

"You know . . . maybe we don't have to give it to human-Controllers," Cassie said. "l don't know why it didn't occur to me before. But it's the Yeerk that can't resist the stuff, right? So why don't we dump it right in the Yeerk poo! itself?"

"Would it work?" Tobias wondered. "l thought all Yeerks ate was Kandrona rays. Do they even have mouths?"

"Yes," Ax said. "Yeerks have mouths. Or what humans would think of as mouths. Actually, if I remember my exo-biology classes, and sadly, I sometimes -"

"Fell asleep," I said. "Yeah, we know. You didn't like exo-biology class."

"l didn't fall asleep," Ax said, sounding injured. "i merely let my mind wander, and became very calm and restful and not completely alert."

"Did you snore when you got all calm and restful and not completely alert?"

"The point is, on occasion I would pay some attention in class. And I believe that Yeerks have something called osmosis nodes. It's what they use to absorb Kandrona rays, but they absorb other nutrients as well.