THE NEXT MORNING, we had so much stuff to carry, Benny’s mom volunteered to drive us to school. She dropped us by the flagpole, like all the other moms and dads, and blew Benny a kiss, which he ducked. It was an old routine with them.

“Have a successful day, boys!” she called to us. Mrs. Brackman is one of those up-with-people people, always saying things like, “It’s Monday—don’t forget to be awesome,” “Be a warrior, not a worrier,” or “My blood type is be positive.”

It’s nice, I guess. But a little goes a long way.

Benny and I hauled our gear—including his covered pet carrier, which was making suspicious noises—into the flow of kids heading for class. Tina Green fell in beside us.

“Hey, Brackman, Rivera,” she said.

“Hey, Karate Girl,” I said.

Tina had arrow-straight cornrows and braids with beads on them that clicked as she moved her head—tik-tik-tik. She’d also been taking karate lessons since she was three or something, so nobody ever teased her about her hair. Eyeballing our massive collection of bags and bundles, she asked, “You moving in?”

“Yup,” said Benny. “Just can’t get enough of school.”

I shook my head. “Social studies project.”

Tina patted her book bag. “Mine’s in here. You guys might want to consider doing something simpler next time.”

“Yeah.” I traded looks with Benny. “If we could, we would.”

Glancing to both sides, Tina lowered her voice. “Hey, what’s with Mr. Chu? He was acting so weird yesterday.”

“Really?” said Benny. “Hadn’t noticed.”

“Uh-huh.” Tina arched an eyebrow. “’Cause most normal teachers growl and dash across the room in a flash. Riiight.”

“Okay,” I said, “he was a little weird. Maybe it was only a bad mood.” I didn’t know why, but I wasn’t eager to discuss our shapeshifting theory with her.

“Uh-huh,” Tina said again, like she didn’t believe a word. “I’m sure that’s all. Well, if you guys decide to let me in on it, just send a text.”

And she lengthened her stride, pulling away from our weak protests and into the classroom.

“You think she knows?” Benny asked.

“She’d be a lot more worried if she did,” I said.

I noticed that Benny hadn’t volunteered our plans either. I wondered if he, like me, had a secret wish to be the hero, to save the day.

Room Thirteen was about half full. Kids were catching up with friends, doing last-minute homework, and getting ready for another school day. Mr. Chu wasn’t around. But his coat hung on his chair, and his sustainable bamboo briefcase (which he’d told us all about during our ecology unit) sat on his desk.

Benny scanned the room. “Perfect timing!” He dumped his bags by his desk and rummaged through one of them. “I brought a little insurance, in case our you-know-what doesn’t work.”

“Insurance is good,” I said.

Then Benny fished out a spray can with a whispered, “Ta-da!”

“No way,” I whispered back. “You didn’t.”

With a broad smile and a waggle of his eyebrows, Benny hurried up to the teacher’s desk with the canister. I followed on his heels.

“Benny, you can’t—”

“Stand a little more over that way, to cover me,” said Benny. He crouched, shook the can, and began spraying Mr. Chu’s jacket with Doggie-Off—the stuff you use to keep your dog from chewing on furniture and stuff.

Automatically, I moved to conceal him. “Seriously, Doggie-Off? We don’t even know what he’s turning into.”

He lifted a shoulder. “So? If it’s something doglike, or even something that hates dogs, it might work. A good dose might scare the whatever-it-is out of him.”

“Or make him lose his breakfast,” I said. The formula kind of stank.

After soaking the jacket, Benny went on to spritz the desktop. I checked out the room. A few kids were staring at us curiously.

“Enough,” I muttered. “We’ve got an audience.”

Benny pretended to wipe off Mr. Chu’s desk. “And there we go,” he said in a fake-cheery voice. “Spick-and-span.”

“Teacher’s pet,” sneered Tyler Spork, who had just come in.

I didn’t have a comeback, but Benny said, “Cleanliness is next to godliness, and godliness is next to good grades. Jealous much, Tyler?”

Tyler scowled, and we headed back to our desks. Just then, the bell rang. On the heels of the last few students, Mr. Chu burst through the door, a bundle of energy.

“Gooood morning, Monterrosa!” he boomed.

The class started to respond in the usual singsong way, but most of us faltered halfway through our “Good morning, Mr. Chu.”

Why? His hair.

Yep. Bald-headed Mr. Chu now sported a crop of spiky black hair a good three inches long. He looked like a hedgehog that had stuck its paw in a light socket, and he was grinning like a lottery winner.

“It’s another awesome day,” he said, “and I can’t wait to learn something new!” Then our teacher ripped out a long, high giggle. “Let’s get edumacated!”

I turned to Benny. He looked just as concerned as I felt, and the rest of the class wore various shades of confusion on their faces.

Oblivious, Mr. Chu dived right into his first lesson, playing Base Ten Bingo with us like nothing was the matter. Benny and I kept an eye on his Doggie-Offed coat and desktop, but our teacher didn’t even approach them. Instead, he roamed the aisles like a daytime-TV host, occasionally calling out “Bingo!” and giggling.

At the end of the lesson, Mr. Chu finally sat down. His nose crinkled, and he brought it right down to the desktop, sniffing deeply.

“Whew!” He fanned the air in front of his face. “I have to have a talk with the janitor.”

“Or Benny,” said Tyler.

“Or Benny,” our teacher agreed. “’Cause someone unleashed a whole new kind of clean here.” He cackled again, like he’d just said the funniest joke in the world, then plunged into a discussion of our class read, Charlie and the Chocolate Factory.

Clearly, the Doggie-Off wasn’t working.

But on the other hand, Mr. Chu didn’t seem particularly wolfy, aside from the extra hair. He was pretty cheerful. In fact, with all the wild laughter, he seemed a lot like a certain comic-book character. I scrawled a quick note:

Any chance he could be turning into The Joker?

And I folded it up and passed it to AJ, who handed it across to Benny. When Benny read it, he glanced at me and shook his head.

“Benny, you don’t agree?” said Mr. Chu coldly.

“Uh, what now?” said Benny.

“With Cheyenne’s point that our author condemns greed in this story. Are you some kind of illiterate moron? Did you even read the book?” As though his mean switch had just been flipped, our teacher grew flinty-eyed, and his lips peeled back from his teeth in a snarl.

Benny looked like he’d been slapped. I gaped. Had our kindly Mr. Chu just slammed my friend?

“Well?” our teacher demanded. “Are you a mute, too?”

Benny held up his hands in a surrendering gesture. “Um, no. I agree one hundred percent,” he said, voice wavering.

“Then why shake your head?” our teacher barked.

“Um, a fly was bothering me?” said Benny.

“Flies?” Mr. Chu’s snarl disappeared, replaced by keen interest. He sniffed the air eagerly. “Is there something dead or rotten around here?”

“Yeah,” said Tyler. “Benny’s lunch.”

The class laughed. But it was a nervous laughter. Most of us were rattled by Mr. Chu’s bizarre mood swing from Dr. Giggle to Mr. Snide. Our teacher snuffled awhile longer, and then, disappointed, got back to the discussion.

Benny sneaked a glance at me. Worry carved new lines in his face.

I gnawed my lip. Whatever Mr. Chu was turning into, he was no longer the friendly, funny Teacher of the Year we’d come to know and love. Something was rotten, and it wasn’t Benny’s lunch (although to be honest, he ate stuff that I wouldn’t touch).

Benny was right. We had to do something.

Right after recess, Mr. Chu asked, “Who would like to go first with their social studies project?”

I looked over at Benny. We exchanged a tense nod.

I raised my hand.

Showtime.