When my sister, Amy, was in 9th grade, her favorite math teacher, Mr. Marris, leapt from the top story of the humanities building and exploded on the pavement. He did it right as the lunch bell rang when the main quad was at its busiest.

Later, everyone would have a story: a description of the way his arms disengaged from his torso. A spot of his blood on a pair of Converse sneakers that landed from twenty feet away. Words Mr. Marris murmured as he descended through the air.

Ninety percent of it was lies. But high school kids had to entertain themselves somehow.

Of course, no one could top Amy. Amy told us all that she was being haunted. We thought it was a joke at first. She’d always been a little weird. Mommy’s little math genius who’d never been to a sleepover much less gone on a date.

As a seventh grader, Amy had memorized pi to 100 digits. By 8th, she was already taking classes at the high school. In 9th, she was the only freshman in Mr. Marris’s calculus class, and the only one with a perfect grade at the time of his fall.

A week after the fall, when Mr. Marris’s replacement came in, Amy spent the first hour of class staring into space and muttering to herself. Finally, after the sub was sufficiently creeped out, she asked Amy what she was saying.

He doesn’t like the way you’re teaching derivatives, Amy said quietly. You shouldn’t start with real world examples like acceleration and speed. Leave that for the physicists. Start with the pure theory like an actual mathematician, you fucking bitch.

If Jackson Poole was to be believed, she’d practically growled those last words like the chick in The Exorcist. But then again, he was stoned half the time and loved making shit up.

After Amy’s outburst, the sub decided to peace out, and the principal pulled Amy out of the class. My parents threw a fit, but the administration wiggled out of their crosshares by claiming Amy was too advanced and needed special accommodations.

The principal got a PhD student from the local college to come in for a couple of hours a week to work with Amy. But the guy freaked out after just a couple of sessions. Every new concept he introduced, Amy seemed to already know back and forth, despite the fact that she’d never read any of the textbooks.

I still have a copy of the email he sent the school with my parents cc’ed: There’s simply no way a 14 year old girl would be able to intuitively grasp Taylor and MacLuarin series through osmosis, sheer genius or even poking around on the internet. Worse, she claims that Mr. Marris is the one whispering answers to her, and that he doesn’t like my cologne. I feel threatened, and I don’t wish to continue in this position.

Of course, to my parents, the school was the problem. Their little genius was just too smart for the lazy administrators. At dinner, they muttered about lawsuits and taking the GED, applications to MIT and CalTech.

“They’re wrong, you know,” said Amy one day after mom and dad had cleared out. “I’m not that smart. He just won’t stop shouting the answers at me. And if I don’t repeat what he says, he gets so mad.”

“I’m sorry,” I said, trying to be comforting. “I guess I didn’t realize you guys were that close.”

“We weren’t!” she shouted. Then, calming down a bit, she added. “You believe me, right? That he’s here? He says you don’t believe me.”

“I think you’ve been traumatized,” I said, careful with my words.

“He said you wouldn’t believe me,” Amy muttered. “He said no one would.”

As I tried to go to bed that night, I heard Amy’s soft snores drifting out from the room across the hall. It had been a long time since she’d gone to sleep before me.

It reminded me of when we were little girls and shared a bed. Back then, her room had been our room. When she had trouble sleeping, she’d stare nervously at the ceiling, conjuring invisible monsters, and I’d tell her stories to calm her down.

I guess we’d drifted apart since then. I still loved writing, but I wasn’t much of a student. At some point, people had decided I was average and she was the star, and those labels had just stuck, pushing us further and further apart over the years. And of course I still loved her, but it had all been shaded with resentment and hurt.

But now, in this moment, I just wanted her to be a star again. To be her old nerdy self. To be okay.

I walked over to check on her sleeping. That’s when I saw the brown book for the first time. She had it nuzzled under her arm as she slept. It smelled musty, and its bindings were cracking with age. Slowly, I crept over and removed it from under her arm.

Mathematica Imaginari read the title.

The book felt strangely warm to the touch, and something in me wanted to drop it. Still, I might have opened it if not for the fact that at that exact moment my sister’s mirror fell off the wall and shattered into a thousand pieces.

Amy woke with a start and looked at me with panicked eyes.

“My book,” she said, springing out of bed. She snatched it out of my hands. “You need to stay away from it,” she warned. “You wouldn’t understand it.”

It was only then that she realized she was standing on a shard of glass. She bent over and pulled it slowly out of her foot.

“Bad luck,” she said, looking dazed. “Seven years bad luck for both of us. Seven times seven is forty-nine. Times seven again is three hundred and forty three. Times seven again is two thousand, four-hundred and one. Times seven again is–”

I screamed for my parents.

After that, Amy took a turn for the worse. She’d take a pen and stand on a chair in her bedroom. Starting at the corner where the wall met the ceiling, she’d scribble impossibly complex formulas, sometimes including symbols I couldn’t identify even on a Google search.

“It’s a proof,” she tried to explain. “A proof of something that humans aren’t supposed to understand, I think. But he’s making me understand. He says we’ve lived in a house of straw called believe for millenia, and this will rewrite everything. The whole house is coming down. There are just so many numbers, though. Holding it all in my head… it’s so hard.”

She was crying as she spoke.

“He won’t stop talking. Won’t stop ranting. He never listens. He never shuts up.”

When we sent photos to professors at the local university, they dismissed it as numerical gibberish, a bucketful of meaningless equations.

“He’s making me do it,” said Amy, almost in tears one day when I asked her to stop. “He says we’ve got to bring the math from where he is back over here. He says his mind is open now. He says he’ll hurt you and mom and dad if I don’t do everything he says. Now I need you to call Professor McAddams at Princeton and tell him the following.”

“Amy–” I started to say. I noticed the brown book at her feet, and I quickly snatched it up.

“I don’t think you should have this anymore,” I said.

Her eyes grew wide and she lunged at me, trying to grab it back.

“Please,” she said. “He’ll make me hurt you. Please just leave before–”

“It’s all in your fucking head!” I shouted. “He’s not making you do anything!”

“Don’t you dare disobey me, you whore!” she shouted, and then she stabbed my hand so hard with the pen that the tip stuck out my palm.

“I’m so sorry,” she said, again and again. “He made me do it! You believe me, right? You have to believe me!”

After that, they had Amy committed on a 48 hour involuntary hold at the psych ward. I wanted to visit, but the doctors recommended against it.

At home, the pain in my hand seethed. My parents were exhausted and went to sleep early, but I just sat in Amy’s room. The brown book lay on the floor, a splotch of my blood still on it for where I’d been stabbed.

For a second, I was furious, thinking about the way she’d stabbed me, how angry she’d gotten. It was like I didn’t know her anymore. But the more I thought about it, the more I just missed her. I just wanted her back.

I picked up the brown book and took it to the stove. Then I put I turned on the burner and let the flames eat the whole cursed thing. The cover stunk and smoked as the flames consumed it. Before it fully went up, I swear it tried to move, edging its way away from the flames, but I put it back in place with a long fork. I kept watching it burn until the smoke alarm went off and my parents ran down panicked to check on me.

Back at school almost a month had passed, and the administration had just gotten its act together to start planning a memorial for Mr. Marris. Posters were up all over campus, complete with his school photo and a request for speakers who had touching memories to share.

I was walking down the hall when I saw Janet Cassidy rip down one of the posters and shove it in the trash.

“Not a fan?” I asked.

“Just forget it,” she said, heading down the stairs. But I followed.

“I thought everyone loved that guy,” I said. “He’s was like, everyone’s favorite math teacher.”

“Come on,” she said. “Don’t play dumb. You’re really going to make me say it?”

“Yeah?”

She shrugged. “He was tutoring me after school sophomore year and felt me up a little. He told me not to tell anyone, so I didn’t. I’d write him little love notes and imagine all kinds of crazy shit. Like how he’d leave his wife for me, and we could finally be officially a couple once I graduated.”

We came up to another poster, and she tore it from the wall, ripping it into pieces, letting them fall to the floor.

“Then one day I walked in. I’d brought him a coffee and asked him for a kiss. But he was busy reading this super old math book. He was muttering numbers, and then he wrote this crazy equation on the board. He asked me to help him solve it, but I wasn’t even in Algebra II yet. Then he called me a fucking stupid kid. I tried to hold his hand, and he basically shoved me off into a desk. That was kind of the end for us.”

“I told a couple of people about the whole thing, but no one believed me. Mr. Marris’s wife was smoking hot. Why would he bother with some ugly underclassmen. People said I didn’t even have boobs to grab, that sort of shit. Even my parents said I should just drop it. The worst part is he told me no one would believe me, and he was right. That without proof nothing I said mattered. Asshole.”

After two days, they let Amy out of the psych ward. Apparently, she’d been able to keep it together pretty well, and the doctors wrote the attack off as an isolated incident. They gave her the number of a therapist and sent her home.

“You burned the book,” she said when I tried to go in to her room to talk with her.

“I thought maybe it would help,” I said. “I just want you to be better.”

“Don’t you get it?” she asked. “It doesn’t matter. He has his own copy over there. He’s going to keep reading it to me. He’s going to keep read it until the numbers take me, just like they took him”

“Amy,” I said. “Mr. Marris is dead. He’s not talking to you. Please. Please come back to me. I just want things to be like they were.”

“He’s laughing at you now,” she said. “He said you set off the smoke alarm. He said now our parents think you’re crazy too.”

“Fuck you,” I said, slamming the door behind me.

We all tried to pretend everything was normal.

Amy even went back to school, but of course by then the rumor mill was going full speed. The abuse was endless.

“So does Mr. Marris watch you go to the bathroom?”

“What’s 2,758 x 9999?”

“Does his wife know he’s with you instead of her?”

“None of them believe me,” said Amy at lunch, crying hot tears that fell from her face all the way down to her lap. “Why won’t anyone believe me?”

I said nothing, staring at my wounded hand.

“Do you know Janet Cassidy,” I asked, but by the Amy was already walking. She marched past the picnic tables and up the stairwell, muttering to herself.

No, I’m done talking to you. I’m done. You can get yourself a new girl. I’m done. I’m done I’m done I’m done!

I started after her, but she was going faster now, taking the stairs two at a time, counting them as she went. She sprinted up, three, four flights of stairs and then up to the roof. I could barely breathe as I tried to catch up to her. Finally, I emerged onto the roof myself to see her standing fifty feet away at the ledge overlooking the quad.

“Wait!” I shouted. “Don’t do this, Amy. I love you! Please don’t do this. I love you so much.”

“I don’t care if you love me,” she shouted back. She leaned out into the space above the quad. If not for the wind blowing her back, I think she might have a fallen right then. “Plenty of people love me! I don’t need that!”

“He’s waiting for me down there,” she shouted. “He’s got a pen all picked out. He says I’ll be holding it for all eternity, writing for him. Holding his fucking pen!”

And then, suddenly, the words burst out of me. “I believe you.”

She blinked away tears.

“No you don’t,” she said. “Don’t lie. You think I’m fucking crazy.”

I took a step toward her.

“I believe you,” I said again, and I meant it. I knew there was no evidence. No way to ever prove it. But I knew she needed someone to believe her. And so that’s what I gave her.

As I said the words again, she fell to her knees sobbing. I ran to her and held her in my arms, just like I had when she was a little wiggly toddler, and all she wanted was for me to hug her.

“I felt so alone,” she said.

I looked around. “Is he here right now?”

Amy blinked her eyes and looked around, confused.

“It’s the strangest thing,” she said. “He’s gone.”