Watching Kermit stir the Monster Blood, Evan suddenly had a heavy feeling in his stomach.

We’ve done it, he thought.

We’ve opened another can of Monster Blood.

He stared at the yellow dough in the bowl. It made a soft plopping sound as Kermit pushed the wooden spoon through it.

Now what? Evan wondered.

Now what’s going to happen?

Kermit stirred the yellow dough. The big wooden spoon scraped the bowl. The doughy mixture plopped softly, tumbling and swirling as Kermit worked.

Andy kept nibbling her lower lip, her eyes locked on the bowl. Her brown hair fell over her face. But she made no move to push it back.

Evan watched from the other side of the table. His heart began doing flip-flops in his chest. He took another bite of the chocolate bar.

He chewed as quietly as possible. He didn’t want to disturb Kermit. As he chewed, he stared at the bowl.

He and Andy were waiting. Waiting to see what the little hunk of Monster Blood would do to Kermit’s mixture.

Waiting to see the look of horror on Kermit’s face.

Waiting to pay him back for being such a little monster.

Kermit didn’t seem to notice how quiet it had become in the basement. Dogface came lumbering in, panting loudly, his paws thudding on the tile floor.

No one turned to look at him.

The dog hiccupped, turned, and padded out of the room.

Evan bit off another chunk of the candy bar.

Kermit stirred, humming to himself. The spoon scraped the side of the bowl. The dough slapped against the edge.

And spilled over.

Kermit stopped stirring. “Weird,” he muttered.

Evan’s heart did a flip-flop up to his throat. “What’s weird?” he asked.

“It grew,” Kermit replied, scratching his white-blond hair. “Look.”

Kermit pointed to the yellow dough with the wooden spoon. It plopped up over the top of the bowl.

“It—it’s growing really fast!” Kermit declared.

Evan took a few steps closer. Andy leaned down to get a better look.

The dough rose up, shimmering and quivering.

“Wow!” Kermit cried. “It wasn’t supposed to do this! It was supposed to turn sticky and black!”

Andy winked at Evan. Her brown eyes lit up excitedly. A smile spread across her face.

The yellow blob quivered up over the top of the bowl, as big as a beach ball.

How big was it going to get?

“Oh, wow! This is awesome!” Kermit declared.

The dough shimmered higher. Wider.

It rose up high over the bowl. It overflowed the sides.

Bigger. Bigger. It started to look like an enormous hot air balloon.

“It’s taller than me!” Kermit declared. His voice had changed. He didn’t sound excited now. He was beginning to sound frightened.

“We’d better stop it, I think,” he murmured.

“How?” Andy asked. She stepped out from behind the lab table and joined Evan on the other side.

Andy grinned at Evan. She was enjoying the expression of fear on Kermit’s face. Evan had to admit he enjoyed it, too.

The ball of yellow dough shimmered and shook, growing bigger every second. It bubbled up faster and faster, pressing Kermit back against the basement wall.

“Hey—help!” he sputtered.

Andy’s grin grew wider. “He’s terrified now,” she whispered to Evan.

Evan nodded. He knew he was supposed to enjoy this. It was supposed to be sweet revenge.

But Evan was terrified, too.

How much bigger would the huge yellow blob grow? Could they stop it? Or would it grow and grow and grow until it filled the entire basement?

“Evan—help me!” Kermit cried. “I’m trapped back here!”

The dough began to shake harder. It bobbed up against the basement ceiling.

Evan glanced down and realized he was still holding a chunk of candy bar in his hand. The chocolate had started to melt.

Evan started to pop the candy into his mouth—just as the giant dough ball exploded with a deafening roar.