“Where are you from, anyway?” Sue asked. “You really don’t seem like you’re from around here.”

“Is this still because I don’t have a chainsaw?” Charlotte asked.

They had taken what Sue said was a shortcut through a back room, more like a long alleyway. There were bare floorboards and plaster walls, littered with pens, crumpled paper, and bow compasses. Above them was a skylight; with the angle of the sun, they could see motes of dust dancing in the air overhead.

“Speaking of which, there’s a locker by the cafeteria. We’ll get you both equipped when we get there. But I meant the way you keep looking around at everything, like you’ve never seen a touchscreen before.”

“Oh,” Charlotte said.

Sue paused. “Am I touching a nerve?”

“You … no, it’s fine. I’m from across the railway line.”

“Oh,” Sue said.

Charlotte winced.

“Not that it’s a problem,” Sue said hurriedly, making a gesture that was meant to be reassuring but which actually turned out more like jazz hands. “I just didn’t expect it. It’s hard to get to here from there, is all. Isn’t it a thing that most people never do, they spend their whole lives there? It means you’re special that you did.”

“I don’t feel special,” Charlotte said.

“Join the club,” Sue said. She motioned, and they both started moving again. “Because if you’re the only person who came here from there, then you’re unique, which means you’re so special that literally no-one else is like you. Well, except your brother, I guess. That’s something I figured out within five minutes of meeting you, in which you haven’t actually said much. And I’m pretty awful at picking up social cues, and you’re quiet.

“What you actually mean – correct me if I’m wrong – is that you know you’re special, or your circumstances are, but you don’t think it’s worth celebrating. It’s like being in a wheelchair. If you are, then you’re special, but in a bad way: most people can walk, but you can’t. Maybe you make the best of it, but even the most handicapable person only brings themselves up to square one. It’s not like being the best at something, where people look up to you.

“As for me, I’m the only half-Chinese in the school. I’m also the only girl of four siblings, and just about the only girl in half my classes. There are, like, four other things like that I’ll tell you about later. What I think is that everyone has something like that. Like, imagine everyone has a unique colour. You can be pink,” she said, looking at Charlotte’s shirt, bag, and ribbon. “I’ll be blue, and Bright is red. Does that make you weird, because you’re not a primary colour?”

Charlotte blinked and waited for a few seconds, checking whether this was a break she was expected to fill. “Does it?”

“Well, let me ask the same question a different way. Pink is a variant of red. Does it make me weird, because blue is the only one of those colours that isn’t red or reddish? And red is the only one of those colours that isn’t pastel.”

Charlotte looked at Sue’s fuku, which was navy blue, not pastel.

“Hypothetically,” Sue said, waving the detail aside. “The point is that it’s easy to come up with dumb patterns that exclude people, so easy that it’s meaningless. For any element of any set, you can say that that element doesn’t belong to, open brackets, the set minus that element, close brackets. It’s true for every member of every group, so that means that it isn’t important for any member of any group.”

“Are you saying that I’m not special after all?” Charlotte asked.

“In your case? Yes, and it’s in the good way. Coming here from across the line is hard, and you did it. It means you’re stronger than you think you are. If ever I want to do something hard, I’ll ask you for advice, same as how I’d ask the gay guy for advice in home eco. If I did home eco. I’m not a 1950s housewife.”

Charlotte normally would have been more talkative, but she preferred to keep quiet while she figured new people out. Sue hadn’t talked anywhere near this much in front of Roger; clearly she was the kind of person who behaved differently around different people. Perhaps she was just nervous because he was an older boy.

“What are your brothers like?” Charlotte asked.

“The opposite of yours, I think,” Sue said. “You know how, if there’s a group of girls, they’ll sit around talking about boys, but boys will decide to build a treehouse together? They do stuff like that, but I usually don’t get invited. To be fair, it’s partly because they’re all older than me. It’s hard to relate to someone who’s three to ten years younger than you. So I don’t really know a lot about them, considering.”

Charlotte had never really considered the idea that a person could become lonelier if they had a larger family. “Oh. I’m sorry.”

“It’s no big deal.”

“What about your parents?” she tried.

Sue shrugged. “Dad runs a restaurant. He’s a pretty good cook; I’ll treat you sometime. Mum works for the government, department of vagueness. Something to do with foreign embassies, I think? She never talks about it. What about yours? You said your mum worked here?”

“It’s nothing like owning a restaurant or working at an embassy,” Charlotte said.

They passed through the door at the far end of the room, into a futuristic room with white plastic walls, floor, and ceiling, lined with computer monitors. Every screen showed boxes falling down from the top, packing themselves away at the bottom, and scrolling down, similar to Tetris. The floor was covered with scraps of plastic wrapping, styrofoam, and popped bubble wrap.

At one computer was a chubby boy with neck-length light brown hair, wearing black slacks and a button-up coat with a high collar. He had a heavy steel chainsaw slung over one shoulder. He looked like he’d been working at the computer, but he’d turned around at the sound of the door opening.

“Hey, Sue,” he said.

“Hey Jason. This is Lottie. We’re BFFs now.” Charlotte went light pink. “You’ve been replaced.”

“That was quick,” he said, then, to Charlotte, “You treat my little girl right, you hear me?”

“We’ve got a new teacher too, a Mr Abercrombie who insists on being called that. We left him with Bright.”

Jason raised his eyebrows. “Then I hope you also brought a spare.”

“She’s not that bad,” Sue said, but not very forcefully. “Anyway, it looks like we might be able to make some headway. Let’s find Blank and get our study on.”

He swiped at the nearest computer monitor, and the boxes, instead of neatly piling up, spun and crashed against each other and broke apart. The words YOU SUCK flashed on the screen, but he’d already turned away, walking toward Sue and Charlotte.

“Sounds good,” he said. “She was checking out the ‘saw inventory.”

“Convenient. Lottie and Mr Abercrombie need one each.”

“You, er, thinking of washing up while you’re there,” he asked, “or is this going to be a gore-soaked waifu dress day again?”

“Again?” Charlotte repeated.

“Give me a break,” Sue said, rubbing the back of her head. “I just got here.”

They went through another door that led to a little courtyard, long and narrow like a hallway and covered in bathroom tiles but open to the sky; with four-storey walls on all sides, it was reduced to a narrow blue rectangle above them. They passed a vending machine full of calculators and dictionaries and came to a red brick shed with a broken padlock.

Sue pushed the door open. Inside was like a warehouse with a double-height ceiling. Cardboard boxes and wood-and-metal shelves lined the floor, arranged into squares so that a person could walk around them. Most of the boxes were taped shut; one was open, with a sea of foam peanuts around it. The shelves were lined with chainsaws and spare parts. There was a fuel tank in the back, together with a row of oil drums and even power outlets and batteries for children’s weak electric chainsaws.

A girl with long, dark, curly hair stood beside one shelf, looking back and forth from the chainsaws to a clipboard. Her outfit combined a mechanic’s stained coveralls and steel-toed boots with the dark grey shirt of a martial arts uniform, cinched with a black cloth belt tight enough to show off her narrow waist. She didn’t deal well with all the oil: her hands and clothes were spotted black, and her hair was frizzing out.

She turned as they entered, very gracefully considering her footwear. “Hiyo, Wong, Fisher,” she said. “Erm. Pinkie.”

“I’m not that pink,” Charlotte mumbled.

“This is Lottie,” Sue announced. “Abercrombie, if you insist on doing the stuffy upper-class private school thing.”

“And this is Blank,” Jason said to Charlotte of the new girl, deadpan. “Among other things, head of the chainsaw martial arts club.”

“Pleased to meet you,” Blank said to Charlotte. “Do you have one of those pocket chainsaws, or are you here to get a proper one?”

Sue snorted. “What, for in case she runs into some particularly wet tissue paper? A real one, please.”

“Welp, you’ve come to the right place. Just in time, too, someone’s been stealing supplies. The gunsaw’s missing.”

“This is why we can’t have nice things,” said Jason.

Blank looked Charlotte up and down, then focused on her arms. She wasn’t exactly buff. “You look like you want something lightweight with good power, not so much focus on tank size or penetration. Come here a sec.”

She led them between the boxes and shelves to one with unpainted chainsaws, took one off, hefted it, and handed it to Charlotte. It was lighter than it looked.

“That’s made of aluminium,” Blank said. “A lot of boys use steel, but I think girls should go aluminium or upgrade to titanium if you want to go further.”

“So, we actually had two reasons for coming here,” said Sue. “No, three. This, I need a shower, and we’ve got a new teacher.” She motioned the others to stay where they were, while she moved toward a side door with the universal sign for male and female bathrooms.

“Really!” said Blank. “Way to bury the lede. Never mind this then.” She took a chainsaw for herself, hung it from her coveralls, and stuffed the clipboard behind the small of her back. “Grab some fuel, Abercrombie, and let’s see what this guy’s made of. Erm, is he a guy?”

“Yes. But he’s not literally made of Keycard,” said Jason, “so you might want to pace yourself.”

“What do you mean, Keycard?” said Charlotte, finding a sash to tie around her waist and hang the chainsaw from.

“It’s why we bother showing up,” he said. “It’s something hidden somewhere in this school, behind all the puzzle door locks. Or, some of them, we don’t actually know which. Honestly, we don’t know much about it. What we do know is, those doors are all kind of pointless; you go through them and get a door with a harder lock. The Keycard is what opens the important doors. Once we find it, we’ll be able to get out of this crummy school for good.”

“We’ve been searching for years,” said Blank. “We don’t know where it is for sure, or even what it looks like, but between us, we’ve got the major connections mapped out pretty well. With your brother leading the way, we should be able to cover a lot more ground. Our last teacher only knows about a fifth of the school, and the locks there are partly random. Either that, or he’s just completely hopeless.”

“Are you sure it’s real?” Charlotte asked. “If you don’t know what it looks it, it might not be. Or it might not work any more.”

“If it isn’t real, we’re probably done for either way,” said Jason. “You stay here too long, eventually the raptors will catch up to you. So, no pressure.”