Robexor’s mighty robotic fist smashed through the wall of the elementary school. Children screamed as the giant robot, over ten feet tall, stooped to stick his head into their classroom and, with a voice amplified by deafening megaspeakers, shouted “Go to your gymnasium for an assembly!”

Little Butch Darby wet himself and tried to run, right past the robot, through the hole in the wall. Before he could get anywhere he collided with an invisible force and fell backward.

The robot grabbed the boy by his shirt and dropped him back in the classroom. “You can not leave this school. I have surrounded it with a forcefield and only by cooperation with my demands will it be removed. Now go to your gymnasium in an orderly fashion.”

And with that the robot withdrew. A moment later Mr. Moore heard the mighty fist smash through the wall of the next room and repeat his demand to another group of students. He stood up (he had fallen down behind his desk) and looked at his stunned and frightened students. “I suppose we had better do as he says,” he said. “Gather your things and go single file to the gym. I’ll be with you in a moment.”

As Mr. Moore heard the mighty fist of Robexor smash through a third classroom wall, he rushed into that room.

“Robexor,” he said. “Stop smashing walls! I’ll get everyone to go to the gym, just stop smashing the school!”

The robot hesitated, then spoke. “Okay.”

Ten minutes later the teachers and the student body was gathered into the gym where the robot towered over them. Mr. Moore got the kids to sit on the floor and Robexor addressed them.

“Somewhere in this school there is a shapechanger. A shapechanger who has pissed me off.”

“Ahem,” said Mrs. Hargrove. “Language.”

The robot sighed. “A shapechanger has angered me and the sensors in my computronic mind tell me that he is in his school. In all likelihood he is posing as one of you, but I can not pinpoint who he is. You will produce him for me or I will be forced to destroy you all.”

Several children screamed and teachers tried to calm their classes. Mr. Moore approached the robot. “How are we to find a shapechanger?”

“It doesn’t matter to me how you find him. I prefer not to harm you humans when it isn’t necessary, but my tolerance for your laws is superseded by my ire. I’m giving you this chance for your benefit. Not mine.”

Mr. Moore looked out over the students. Mrs. Hargrove joined him. “What are you thinking?” she asked.

“We’ve got to work it out, I guess. We have to figure out who this shapechanger is.”

“If we stall the robot long enough, the police will save us.”

Mr. Moore remembered the first time he saw Robexor on the news. Footage of the robot carrying a tank in each hand and flying over the Grand Canyon and shooting a laser at the army below. “I don’t think they police could do anything to save us. We should try to do what Robexor wants.”

“But how?”

Mr. Moore turned to the robot again. “When did this shapechanger come here?”

“Within the half-hour.”

“Then he’s not been here since the start of the school day. There aren’t any new students or teachers here, so he is in the form of someone who belongs here. If he’d come in at the start of the day I’d say he could have taken the form of some student who was sick or something. But in this case, the person he replaced must have been here before he replaced them. Maybe we should check the bathrooms or lockers to see if any students or teachers are tied up.”

“My sensors say that all living humans are in the school are in this room.”

“My God. Then he could have killed someone to take their place. But classes have been in session for the last hour, so he would have had to get someone who was alone…” he paused and pondered. Turning to the teachers, he said “Okay, within the last half-hour, how many of you let a student go to the washroom? Or out of class alone for any other reason?”

And soon Mr. Moore had a list of three students who had been briefly alone during the last thirty minutes. Mr. Moore brought those three to the front of the room.

“Tina LaFitte,” he said looking down at the first of the trio, a dark-haired seven-year-old clutching her books nervously to her chest. Mr. Moore had taught her the previous year. “If you’re really Tina, you’ll know what book you did your report on in my class last year, right?”

“The… the Adventures of the Wonderful Puppy,” she said.

Mr. Moore smiled and said “That’s right! You can go sit down.”

As Tina happily ran back to her friends, Mr. Moore turned to the next child. “Arnold Thomas.”

The boy looked up at him through thick glasses. “I’m really me.”

Mr. Moore had met Arnold when he moved to this school just a month ago. “You told me once, Arnold, what the name of your fish was that you had to leave when you moved here. What was his name?”

“Chompy!”

Mr. Moore clapped the boy on the shoulder and said “Go sit down, Arnold!”

The last boy, an eight-year-old blond boy that Mr. Moore has never taught, was sweating.

“Harvey Boltz. What name did Butch Darby call you last year that made you cry?”

“I don’t want to say it.”

“I’m sorry, but you have to or the robot will kill us all.”

“He called me Dumb-head McBum-head.”

The students laughed as Harvey stomped back to his spot. Mr. Moore rubbed his forehead as he tried to think of another possibility. The robot, who had been sitting cross-legged behind him stood back up.

“Wait!” said Mr. Moore. “Wait, Robexor. We know that none of the students are the shapechanger, surely you could lower the forcefield and let them go and just keep the adults.”

“No. I won’t risk it,” said Robexor. “Now hurry this along.”

Mr. Moore debated what was to be done next. Maybe one of the teachers had left class for a moment to wind up killed and replaced? But to him that seemed unlikely. Why would a shapechanger take one of the most high-profile positions? As a teacher any strange behavior would be noticed quickly when they didn’t know how to keep teaching class. What about the rest of the staff? The Principal had been out getting lunch. The janitor wasn’t here, so he must have been outside the school as well. Asking, he learned that the school nurse and the receptionist had been hanging out for an hour watching videos of cats on the computer and could vouch for each other not having been alone. That left only one possibility.

“Robexor,” said Mr. Moore. “I think you’ll find that the impostor has taken the form of Vice-Principal Bill Stoves.”

“What?” gasped Stoves. “I’m not the one!”

“You’re the only possibility! Get him Robexor!”

“Mr. Moore,” said a tiny voice from the back of the room. “Mr. Moore!” Susie Bolton stood up.

“What is it, Susie?”

“That soccer ball in the corner just sneezed.”

Robexor reacted instantly. Jumping across the room, he shouted “Changer! I’ll kill you for writing ‘Robexor is Dumb’ on that truck!” and the soccer ball morphed into a humanoid form screaming “Ohhhhh Shiiiiiiiit!”

The duo crashed through the wall of the gym and their fight raged across town.

“Oh,” said Mr. Moore. “Or he was the soccer ball. I would have gotten that eventually.”

Patrick D Ryall, the D is for Helmet