EMMET WAS SURPRISED THAT THEY MADE IT OUT OF THE gym, convinced as he was that they were going to die inside it. The only thing preventing him from doing a happy dance was the fact that the hallway was full of Blood Jackets as well. Maybe even more than there were in the gym, if that was possible.

“Where in the world did all of these things come from?” he shouted over the noise of the fire alarm. A Blood Jacket flew at him, landing on his football helmet, and Raeburn deftly flicked it off with her stick.

“Probably nested in the ventilation system,” Calvin said matter-of-factly as he swatted another creature that was headed for Riley out of the air.

“Really, Captain Obvious?” Emmet complained. “So, which way do we go?”

Tasker Middle School was designed like a giant letter H. They were in the hall outside the gym. It connected the two large hallways that ran parallel to each other. If they went to their right and then left down the main hallway, they could exit the building and hopefully escape these horrifying creatures.

“This way,” Riley said. “There’s an emergency door right around the corner.”

They followed her lead and went left instead. Emmet was thinking it was smart of her to remember the fire doors. TO BE USED IN THE EVENT OF AN EMERGENCY, the signs said. He was pretty sure this qualified.

They scrambled around the corner and sprinted to the door. The flying death machines followed them, screeching through the air. Calvin charged headlong at the door and grabbed the handle, coming to a crashing, thudding halt.

“Oof!” he said as blundered into it. He pushed the bar again, and nothing happened.

“Somebody sealed it shut,” Emmet said, pointing. The handle had been secured with a nylon zip tie.

“Who would do that?” Calvin said.

“It’s Dr. Catalyst! He’s here!” Emmet shouted.

“You don’t know that,” Calvin said.

“Yes, I do. My Dr. Catalyst sense is tingling. Who else would do this? Come on, we’ve got to get out of here.”

The four of them ran down the hall to the next emergency exit, only to find it was also sealed. Emmet swung his stick at the zip tie in frustration, but it had no effect.

“We need to find something to cut through these. I don’t suppose you have a jackknife in your sock?” he asked Calvin.

Calvin shook his head. “You’re not allowed to bring knives to school.”

“Come on!” Raeburn said. “Let’s head to the front door.”

They ran back to the center hallway and past the gym doors. Blood Jackets were pouring out of the gym. Emmet couldn’t tell if these were new creatures, or if the rest of the crowd had escaped outside and these critters were flying around looking for new victims. It was hard to keep track because they flew extremely fast and there were so many of them looping around one another.

As they reached the other main hallway, they ran to the nearest emergency door. It too was sealed with a zip tie. Someone had deliberately sealed the doors.

“Who would do this?” Riley cried, her voice thick with desperation. The alarm was still blaring.

“Dr. Catalyst!” Emmet insisted. “He’s here!”

Calvin and Raeburn began swinging their sticks back and forth while Emmet and Riley tried to find a way to open the door. But without something sharp, it was useless.

“The front door can’t be sealed. All of the people at the concert had to get out somehow,” Emmet said.

“We can’t get out that way,” Calvin said. “Look at the doors.”

At the front entrance of Tasker Middle School were double doors made with large safety-glass panels on each one. There were tall floor-to-ceiling windows on either side of the doors. Outside, they could see the flashing lights of emergency vehicles, but only barely. The doors were covered with a moving, squirming wall of the hybrid monsters. And more and more of them were flying at the window, trying to escape the confines of the building and the shriek of the alarm.

“Oh. My. God,” Riley said.

“We better get out of here before those things notice us!” Raeburn said. She and Calvin were swinging their sticks in a wide arc, trying to keep the nearby creatures at bay. Emmet tried desperately to pry the zip tie loose from the door. He had wedged his stick between it and the door handle, but no matter how hard he pulled, the thick plastic would not give.

“It’s no use,” he said. “We need to find another way out.”

As Emmet tried to work his stick free from the sealed door, a strange feeling came over him. Like he was being watched. And not by the tiny flying death machines. He yanked the stick free and stepped back from the door, looking down the hallway in the opposite direction, toward the rear of the school.

A man was standing there, studying them. He was wearing a black Windbreaker, and though there were plenty of Blood Jackets flying around him, they didn’t attack or dive at his head or body. In fact, if anything, they appeared to be ignoring him.

“Look!” Emmet pointed down the hallway, and Riley, Raeburn, and Calvin followed his gaze. The man stared back for just a few seconds, then slipped through the door at the end of the hallway.

“Who was that?” Raeburn asked.

“Dr. Catalyst, I presume,” Emmet said. “And I bet he has a way out of here. Come on!”

The four of them sprinted down the hallway in the direction the man had disappeared. They didn’t notice that the Blood Jackets that had been covering the windows and doors of the school’s front entrance were now alerted to their presence. With a loud shriek, they took to the air and pursued their four victims down the hallway.