The footsteps got louder. And closer. Whatever was coming was moving fast.

I spied a small crevice in the wall. It was barely big enough for a goblin. I jumped in anyway. Tank pushed in behind me. She didn’t get far.

“I don’t fit!” she hissed, stumbling back into the tunnel. “Hold on. Let me get something.”

She rummaged through the pockets on her tool belt.

We waited until the sound of its voice had faded before tumbling out of our hiding spot.

“That was close,” I gasped.

“Too close.” Tank hastily folded the piece of fabric.

“What is that thing? A new invention? Some kind of mechanical camouflage barrier?”

Tank shook her head. “My raincoat. Mom always makes me pack one.”

“Your raincoat! You planned to save us with your raincoat?”

“You’re the one who pulled me into that bug hole!” Tank stared at something over my shoulder. “Your backpack is glowing.” A soft green light showed through the material of my bag.

“Little Scrapper!” I opened my backpack. Safe inside its little container, the slime glowed a calm green. Hutch was right. This thing could sense Snag’s slimes. “We’re getting close.”

A newfound sense of confidence washed over me. I held Little Scrapper’s container close to my chest. Ahead, the tunnel opened to a wide cavern. We crept to the entrance and peered inside.

Little Scrapper lit the cavern wall with a soft glow. The rocks were jagged and sharp, like they’d been hacked out by a blind ogre with a pickax. Bits of pulverized rock lay everywhere. A haze of purple dust floated in the air.

In the middle of the cavern, a blue creature smaller than me skipped around the room, singing.

“Boom, boom! We make room! Boom, boom! Treasure be ours soon!”

It was the monster that had skipped past us. It had large fat ears and a tail that ended in a sharp spike. I’d seen a lot of different monsters in Slick City, but I’d never seen one of these creatures.

On second thought, maybe I had.

“Gremlins,” I said. Icy claws ran down my spine, gripping me all the way to my tail.

“We’ve found the Gremlin Gang,” Tank said in a whisper almost too quiet to hear.

The Gremlin Gang had arrived in Slick City. Mom had said they were on their way here.

It didn’t make sense. Slick City had banks with stacks of money and galleries with priceless works of art. And yet, here was the Gremlin Gang, right under my school.

The gremlin stopped singing and charged to a dark corner of the cavern. He returned with a heavy-looking bucket. He zipped to the middle of the cave and climbed a ladder standing beneath a shallow hole in the ceiling. The ladder looked familiar. On its side were the words Property of Gravelmuck Elementary.

“That ladder is from the school!” I said.

“They’re a gang of antique thieves,” Tank whispered. “Stealing a battered old school ladder is not going to bother them.”

The gremlin teetered at the top of the ladder. One hand carried the bucket. The other held a large paintbrush. He dipped the brush in the can. It came out covered in purple paint. Purple, sparkling paint.

“The purple dust!” Tank said. “It’s in the paint.”

The gremlin spread the paint on the ceiling of the cavern. He hopped off the ladder and dragged it to the far corner. He turned to face the hole in the ceiling and got that look of concentration I’d only ever seen on Aleetha. The gremlin said the same magic words Aleetha had used at the harbor.

The dust on the ceiling bubbled. It shook.

I grabbed the wall. I knew what was coming.

The patch of purple paint exploded. Rocks flew from the ceiling. The entire tunnel shook. It all happened without making a sound.

“That proves the purple dust is the source of the tremors,” I said when my brain had stopped shaking.

“The Gremlin Gang is using the dust to make a tunnel in the rock silently. No one at the school can hear it. But they can’t hide the shaking.”

It made sense. But something else tugged at the back of my brain.

“Why is Principal Weaver telling everyone it’s the heaters shaking the school?”

“Because I told her to.”

We spun around to see the owner of the voice behind us.