It was early one evening.
Principal Penn and the teachers were arriving at Metro City Grand Hotel.
A mysterious man named Mr. Sweeps had invited them to a special meeting.
"Maybe he's going to donate money to the school," thought Principal Penn.
"Welcome," said Mr. Sweeps.
"Please take a button."
Principal Penn pinned a star button onto her jacket.
Then she sat down.
"Now," said Mr. Sweeps.
"Let me tell you why I invited you here . . ."
It was a beautiful fall morning.
Roxy and her friends were walking to school.
"I hope the weather stays like this," said Jack.
"Our class has a field trip to the zoo next week."
"I can't wait to see the snakes," said Terrell.
"I'm worried we won't be able to go to the zoo," said Mara.
"My mom told me our school needs money.
The field trip to the zoo might be canceled."
"That would be awful!" said Jack.
"We should do something to help."
"What can we do?" asked Mara.
"We don't have any money."
"Maybe Rocket Girl can help," said Terrell.
"I don't think so," said Roxy.
"Rocket Girl doesn't have money."
"Rocket Girl can do anything," said Terrell.
"She's the greatest superhero ever!"
Roxy shrugged.
Soon Roxy and her friends reached school.
Roxy looked at the parking lot.
"Where are all the teachers' cars?" she wondered.
"Welcome, students!" said a man at the school entrance.
He was handing out star-shaped buttons.
"I'm Mr. Sweeps, your substitute principal today.
Principal Penn is . . . um . . . busy doing other things."
Roxy looked at Mr. Sweeps suspiciously.
Something about the substitute principal seemed odd.
"Cool! Thanks for the button!" said Jack.
Mr. Sweeps handed one to Roxy.
"Here you go, young lady," he said.
"Thanks," said Roxy, carefully looking at the button.
"Go ahead, put it on," said Mr. Sweeps.
Just then Roxy heard her watch beep.
She put the button in her pocket.
Then she hurried away from the school's entrance.
Roxy pressed a button on her watch.
"Mayor Bloom," she said. "What's wrong?"
"We have a problem, Rocket Girl," said the mayor.
"Principal Penn disappeared.
I want you to find out what happened to her."
Roxy looked over at Mr. Sweeps.
"Don't worry," said Roxy. "I'll find Principal Penn."