Those first few weeks Diane and I were lab partners, I never asked her anything about her dad or her family. Then one Sunday I was out walking the dogs and I spotted Diane and an older man in a suit and string tie at the cemetery over on Fall Road. They were carefully placing a big spray of white flowers on a headstone. The man, who must have been her granddad, hair white as frosting and face tanned and serious, was sobbing, while Diane stood rigidly, arms at her side.

Tugging at his leash, Grimm let out a yowl.

Diane didn’t move, but I kept going. Walked faster, head down.

That night, I looked it up online. The death notice.

There was really nothing there to see except for the blurry photo of a stiff-backed, mustached man trying very hard to smile. And those words passed away unexpectedly, which I guess they always say when you die so young.

By then, Diane and I were studying together almost every night.

I was working harder than I ever had, my calculations telling me I had to get a ninety-seven on my AP Chem midterm to qualify for the Severin scholarship.

No senioritis on you, my mom kept saying, somewhere between wariness and pride.

There was a satisfying, soothing rhythm to it all. Diane with her mechanical pencils and me with my green-capped Hickory Hill Animal Rescue Bics, the two of us exchanging our formulas, checking each other. Diane, pencil tapping on lip, reading over my combustion analysis, and me trying so hard to find errors in hers, any error. The one or two times I did, I could barely bring myself to tell her, not wanting to see that nervous crumpling over her eye, the twist of her mouth.

Sometimes we ran together too. Diane wanted to get her Lanister letter in cross-country to match the one from Sacred Heart. It was funny to think of how much it had mattered when I got mine last year, when I’d never even heard of the Severin scholarship and wasn’t sure I’d take AP Chem because would City Tech really care?

One morning before school, we ran clear to the interstate, where I spotted Tanner and Stacey opening things up at the Golden Fry, its fuzzy neon lights coming on and the smell of chicken fat making my mouth water.

“Looking good, Kitty Kat,” Tanner shouted, big smile gleaming.

“You have so many friends,” Diane said, after.

“Work friends,” I said. “Sometimes we drink out at the old speedway after closing.”

We were breathing hard and I felt the sweat everywhere. We’d run for so long. Sometimes it was like Diane forgot we were still running, her body just moving, always, forward.

“My mom says that’s important,” Diane said. “Friends, dances, parties.”

It was hard to picture Diane hanging out with girls like Ashley G. and Rachael Schreiber, who spent their free time dyeing their hair pink and going drag-racing under the viaduct with Emmet Diaz or Jeff from the taco place or Matt Stollak, who came from Texas and could do backward free throws on one bounce from the far end of the court into the basket.

Walking down the halls, she always seemed a girl apart. All around her, kids might be buzzing and swooping and swinging their bags and waving their phones like bright flags, but she never seemed to belong to any of it.

“But it’s just not that important to me,” Diane said. “Not like the Severin.”

She smiled a little and I smiled too.

I’d have traded Alicia and Rachael and both Ashleys for Diane’s brain. All the friends in the world weren’t going to get me out of Lanister.

Then Diane said the funniest thing.

“Except sometimes I see you walking your dogs,” she said. “You’ve got your earbuds in and the dogs all tangled in your legs, and the way you’re walking, like…like there’s nothing in the world to worry about it. And I think, That’s what I want.”

“But that can be you,” I said. I was thinking of our bull mastiff, Grimm, and Fudge, our German shepherd, and Old Sam, the dog they were meant to replace. When my dad ran over Sam with his Mustang, I cried for three days. I thought I’d never stop crying, my face swollen and pink like an Easter Peep. “Anybody can do that,” I told her.

It felt like she was seeing something in me that she wanted to, something I had that she didn’t. But it wasn’t really a thing I had, or a thing I was. It was just part of being in the world, of living. You cared about things. People, animals. That was what you did.

“I’m going to try,” she said. “I’m going to try to do that.”

“Kit,” Ms. Castro said, waving me into her counseling office one day, “I’m really glad you and Diane have become such fast friends.”

“You mean you hope she’ll rub off on me,” I said, smiling. Ms. Castro never really liked my hanging out with the Ashleys or Alicia or, worse still, wild Michelle Turlock, now transferred to St. Martha’s, with whom I used to duck out of last period to play pinball and smoke cigarettes with my cousin Scott.

But Ms. Castro’s lips became a line, like they did when she had bad news (Your father didn’t send the check for the cross-country uniform or your letter jacket, Kit).

“No, I meant you’re helping her,” she said. “She’s had a hard time. Shuffled around from Mom to Mom-and-boyfriend to Dad. Then he passes away and she’s packed off to her granddad…” She shook her head.

Until that moment, I hadn’t realized Diane had been living with her dad when he died, and suddenly everything seemed so much worse.

“I just want to make sure you understand,” Ms. Castro continued. “A parent dying—it changes a person.”

“Yeah, I know,” I said. “Everything changes you.”

Ms. Castro paused like there was something she wanted to say but wasn’t sure how. Finally, she nodded, pushing her glasses back up the bridge of her nose.

“It can do things to a person,” she said, turning from me. “And sometimes it takes a long time to figure out just what it’s done.”

That night, she came to my house to study, appearing in our driveway behind the wheel of a big truck like the kind wealthy ranchers drove on TV. Seeing her descend from its high haunches in her cream sweater and long braided ponytail was always memorable, like seeing a pale angel alighting from the clouds.

“Whose is that?” I asked, remembering Mrs. Fleming’s speckless white sedan, grille like a tombstone.

“My grandfather’s,” she said. “He lets me take it whenever I want.”

“Do you ever get lonely out there?” I asked. Her grandfather’s house was all the way over in Frontenac, seventeen miles away, on a fifteen-acre place nearly in the mountains.

“No,” she said, curling her fingers around a bunny-paw key chain, so girlish for Diane, and I wondered if her mom gave it to her. “My mom and I talk on the phone every night.”

“My room’s pretty small,” I warned, escorting her through our pocket-size house quickly, the smell of carpet deodorizer and my mom’s Corn Huskers moisturizer, her arms always red to raw from the chemicals at the clinic.

The room seemed even tinier when we both stepped inside, barely space for us both to stand with our backpacks, my narrow bed, plywood desk stacked high with books, a thin strip of carpet between the two.

But Diane didn’t seem to notice, looking around at my goofy dog poster, my running shoes flung over the desk chair. My books wedged tight in milk crates.

“I have this,” Diane said, her fingers touching the crinkling plastic library-book cover of Marie Curie: A Life.

“Do you?” I said, smiling.

Before we started, my mom appeared with a tray of sodas and chips, the thick-ridged kind, and Diane acted like it was caviar and champagne.

“Your mom’s really nice,” she said when we were alone again. She was holding a chip in her hand like it was a baby chick you’d better not squeeze too hard.

“She’s pretty okay,” I said. “You must miss yours. How come she’s not here?”

“She moved to Florida with her boyfriend,” she said, setting the chip down, uneaten. “I decided to stay here to finish school.”

“You guys seemed tight,” I said. “Maybe she’ll come back. She’s gotta come for graduation.”

“Maybe,” she said, turning away, reaching for her bookbag. “I don’t know. She’s always loved the beach.”

It seemed like a funny kind of answer. Then she opened her wallet and flapped it at me: a snapshot of Diane and her mom, two blond beauties with legs a mile long in matching white one-pieces at some pool, that big sparkler I’d seen at camp flashing on her mother’s finger.

“That’s from last summer,” Diane said. “When I visited.”

My mom was only thirty-four and we even liked to swap jeans sometimes, even though it meant her lying back on her mattress and wriggling like a dog tick to zip them up. But I couldn’t imagine the two of us hanging out in bathing suits and getting our picture taken.

There was something in the snapshot—edges curling, a thumb smudge on one corner from so much touching—that made me sad. I wondered if Diane’s mom looked at it half as much.

“Do you wish you were living with her?” I said.

“No,” Diane said, not meeting my eyes.

“Who wants to live in Florida?” I said gently. “Alligators and serial killers.”

“So you’ve met her boyfriend,” she said. And I laughed. Diane had made a joke!

“Parents’ love lives are the worst,” I tried. And I explained how, one night, soon after my mom had kicked my dad out for good, he’d shown up and plowed across the lawn in his blistered Firebird (Cash-poor, hood-rich SOB, my mom would say with a sigh), then went careering into the backyard, uprooting our old swing set by its haunches, like in a video game.

“My dad always hated that swing set,” I said.

“Why?” she asked.

“Broke his leg jumping off the top of it on the Fourth of July,” I said. Then added, “I may have dared him.”

Diane let a sneaky smile appear, the rarest of things.

“You should’ve tried it with your mom’s boyfriend,” I said.

“They have nine lives, those men,” she said, more softly now. “Don’t they?”

I nodded. Nothing ever felt so true.

She turned away from me and began removing her books from her bag one by one in the slowest, most methodical way.

“We better start,” Diane said, pointing to my bookbag. “There’s not much time.”

It wasn’t until hours later, both of us jittery on Diet Coke (“My grandfather won’t have any soda in the house,” Diane told me, slurping greedily. “Grandma died of diabetes”), when we’d nailed the last of the net ionic equations, eraser dust flying, that I got up the courage.

“Hey, I saw you on Sunday,” I said. “At St. Bonaventure’s.”

“I saw you too,” she said, surprising me again. I’d never seen her turn her head.

“Whose grave was that?” I asked.

She looked up. “My dad died last year. I thought everyone knew.”

“I wasn’t sure,” I said, my face burning. “People say stuff.”

There was a pause so long I thought maybe she’d never say another word.

“I remember him from when he picked you up at camp,” I said, finally. “He seemed really nice.”

She still didn’t say anything, so I tried to touch her hand, like my mom always did when people’s pets died. But she was cold to the touch, cold as the door to the walk-in freezer at the Golden Fry, and I could tell she didn’t like it.

“I’m sorry,” I said, pulling my hand back. “I mean, about your dad.”

“Thanks,” she said. “We weren’t close.” She paused a second, looking at me. “It’s sad, though.”

There was something so odd about her face, how it didn’t change. The skin smooth as sweet cream and lashes like a doll’s hairbrush.

“A heart attack, right?” I said, scrounging for things to say. “It’s…”

“It’s strange,” she said, nodding thoughtfully. “It’s just strange sometimes that he’s really gone. We didn’t know each other that well.”

“That doesn’t seem strange,” I said.

“He didn’t really know much about being a dad,” she said. “My mom used to say he was a haircut in search of a personality.”

I looked up, surprised. Seeing my surprise, Diane suddenly looked surprised too.

“She didn’t mean it like that. She’s just always wanted me to want to be with her.”

I nodded, but as I did I felt the same faint chill I’d felt watching her at St. Bonaventure. Something in the way her face rested, in the way her hand lay, palm open, on her lap.

“My grandfather put this framed picture of him in my room,” she said. “And every night, I stick it in the bedside drawer. Every morning, I take it out again so he won’t know.”

It was the most she’d ever said about anything other than titrations and scholarship-application deadlines, but she said it in almost the same way, just slightly flatter, the words so matter-of-fact.

“I get it,” I said. “When my grandma died, I used to dream about her standing at the foot of my bed yelling at me. Asking why we put all that dirt in her mouth.”

She looked at me, and for a second, it felt like something was lifting from her as we sat, as if her squared shoulders rose higher and her eyes tugged back from some darker place.

“I just wanted her to go away,” I added, unable to stop now. “But every night, there she’d be at the foot of my bed.”

Both our gazes turned to the edge of the bed, its cramped foot. The dark space behind it, the sharp surprise, though we both knew it was there, of the stick-on mirror on my closet door.

“Yeah,” Diane said, turning away quickly, looking down. “I have those kinds of dreams.”

When she glanced up again, her face looked so tired, like an old woman’s.

“Be careful with that one,” my mom said later, smearing her face with lotion in the bathroom.

I stopped in the hallway, wondering if she’d heard something. “What do you mean?

“Remember that Birman we had for a while?”

The cat with paws like snowy mitts. I was nine or ten, and one day she darted out from under the sofa and chomped me on the wrist. I suffered through a rabies shot and cat scratch fever that made my underarm bulge like Popeye’s. It turned out she’d fractured her ulna and it had made her scared and mean.

“We didn’t know until we did the X-ray,” my mom said. “You had to look really close to see it, but there was the tiniest hairline fracture. Watch for the crack in the prettiest bone.”

“What about the whipworm I got from the schnauzer you brought home so they wouldn’t croak him? Or the second rabies shot I had to get from that old bat?”

“That bat was not my fault,” she said, snapping a tissue from the box, wiping at her hands. “He was hiding in the tire swing.”

“Uh-huh.”

“Listen, Kit, there are some people who are trouble. They can’t help it,” she said, watching me in the mirror. “But let them in, and they’ll swallow you whole.”

I didn’t say anything for a moment, but the hallway felt hot and I wanted to leave.

“Mom,” I said. “I know about those people.”

Besides, there was no time to worry about Diane, especially not when she was helping me. Just being around her made it seem like studying all the time wasn’t a burden but a plan. A way out.

Even now, I’m not sure what drew us closer: these few confidences, a dark sharing, or the Severin. That’s what we called it now. Just “the Severin.”

By December, my AP Chem grade was up to ninety-five, and I had a ninety-six in physics.

“You should be really proud,” Ms. Castro told me. “You’re going to make eligibility, I know it.”

“Don’t jinx me,” I said, crossing myself.

“Just keep going,” Ms. Castro said. “You’ve got this.”

So I kept going. I studied all through Christmas Eve stocking-hanging and my mom’s eggnog-and-tree-trimming holiday-movie sob-a-thon. I even skipped the secret, after-close New Year’s party at the Golden Fry.

In the last few frigid January weeks before midterms, I’d come in the door at eight, and if Mom was home, she’d send me to the shower immediately to wash off the stink of the Golden Fry, especially those nights after I’d bricked the grill and came home slicked in oil and feeling mean. But by half past eight, I’d be elbow-deep in the books.

“Kit, don’t you wanna take a break?” my mom asked me one evening, her night off. “How about we go to Pinky Toes? My nails are trashed from all the Bru-Clean. Oh, honey, I had to hold this rabbit during surgery today. His legs were like a teacup handle.”

But I didn’t want the gel mani. Or to walk the dogs to the rail trails or eat peanut butter and banana sandwiches while watching the tanned women on reality TV.

I didn’t even care when Keith Brandt said I had a banging stride at cross-country that day and maybe we could get together. My stride was banging. Concentrating so much more on everything made me run better, faster. I was thinking all the time.

I was thinking so much, so fast, so hard, that sometimes I dreamed about ionic compounds. Ms. Steen told us a famous chemist named August Kekulé once fell asleep while working on a problem and he dreamed of atoms dancing into the shape of a snake, which then turned around and bit its own tail. When Kekulé woke up, he realized that benzene molecules were made up of rings of carbon atoms, and that opened up an entire new field of chemistry and gave everyone a new understanding of chemical bonding.

What if, I wondered in bed every night, someday I dreamed of something like that?

But other times, it all felt so far away. And seeing all the one hundreds on Diane’s grade sheets, and that thing Ms. Steen said about maybe she should just hand over the class to Diane—sometimes it seemed impossible. The Severin and everything else.

“Maybe it’s not for me. Maybe I don’t care enough,” I told Diane after a rough lab full of screwups and my forgetting to preweigh the flask, throwing off our results. “Not like you do.”

Watching her in class, the way she knew the answer to every question, and the complication to every answer.

“Kit, let me show you something,” she said, opening her laptop.

The screen lit up brilliantly. It was a series of short films shot with high-definition cameras—simple chemical reactions, but magnified, intensified, until they became magical explosions.

“This is my favorite,” she said, showing them adding zinc metal to a lead nitrate solution. In seconds, a silver-tipped winter forest from a fairy tale emerged.

“They put it in a soft gel,” she said, “to preserve it.”

The gel’s bubbles looked like giant globes.

We watched again and again as the glinting and intricate forest seemed to paint itself before our eyes, the simplest of chemical reactions.

If you’ve never seen it, you should.

“Dr. Severin has these cameras in her lab,” Diane said. “These are from her lab. The Severin Lab.”

By this point, her name had become like an incantation.

“You can do it,” Diane said. “Science is facts and results. It’s not messy. It’s precise.” She placed her palm on the cover of her AP Chem book. “Everything makes sense here. It’s the safest place.”

I looked at her. “For people like you.”

“But you are like me, Kit. You’re just like me.”