All I have left of my mother is her research. I pore over her journals, because I know one day the words will rearrange themselves on a page and point me toward her. She taught me, even in absentia, that all good science starts with a hypothesis, which is just a hunch dressed up in fancy vocabulary. And my hunch is this: She would never have left me behind, not willingly.

If it’s the last thing I do, I’m going to prove it.

When I wake up, Gertie is draped over my feet, a giant dog rug. She twitches, running after something she can only see in her dreams.

I know what that feels like.

I try to get out of bed without waking her, but she jumps up and barks at the closed door of my bedroom.

“Relax,” I say, sinking my fingers into the thick fur at the ruff of her neck. She licks my cheek but doesn’t relax at all. She keeps her eyes fixed on the bedroom door, as if she can see what’s on the other side.

Which, given what I have planned for the day, is pretty ironic.

Gertie leaps off the bed, her wagging tail pounding the wall. I open the door and let her scramble downstairs, where my grandmother will let her out and feed her and start to cook breakfast for me.

Gertie came to my grandmother’s house a year after I did. Before that, she had lived at the sanctuary and she was best friends with an elephant named Syrah. She’d spend every day at Syrah’s side; and when Gertie got sick Syrah even stood guard over her, gently rubbing her with her trunk. It was not the first story of a dog and an elephant bonding, but it was a legendary one, written up in children’s books and featured on the news. A famous photographer even shot a calendar of unlikely animal friendships and made Gertie Ms. July. So when Syrah was sent away after the sanctuary closed, Gertie was just as abandoned as I was. For months, no one knew what had happened to her. And then one day, when my grandmother answered the doorbell, there was an animal rescue officer asking if we knew this dog, which had been found in our neighborhood. She still had her collar, with her name embroidered on it. Gertie was skinny and flea-bitten, but she started licking my face. My grandmother let Gertie stay, probably because she thought it would help me adjust.

If we’re going to be honest here—I have to tell you it didn’t work. I’ve always been a loner, and I’ve never really felt like I belong here. I’m like one of those women who read Jane Austen obsessively and still hope that Mr. Darcy might show up at the door. Or the Civil War reenactors, who growl at each other on battlefields now spotted with baseball fields and park benches. I’m the princess in an ivory tower, except every brick is made of history, and I built this prison myself.

I did have one friend at school, once, who sort of understood. Chatham Clarke was the only person I ever told about my mother and how I was going to find her. Chatham lived with her aunt, because her mother was a drug addict and in jail; and she had never met her father. “It’s noble,” Chatham told me. “How much you want to see your mother.” When I asked her what that meant, she told me about how once her aunt had taken her to the prison where her mom was serving her term; how she’d dressed up in a frilly skirt and those shoes that look like black mirrors. But her mother was gray and lifeless, her eyes dead and her teeth rotted out from the meth, and Chatham said that even though her mother said she wished she could give her a hug, she had never been so happy for something as she was for that wall of plastic between them in the visiting booth. She’d never gone back again.

Chatham was useful in a lot of ways—she took me to buy my first bra, because my grandmother hadn’t thought to cover up a nonexistent bosom and (as Chatham said) no one over the age of ten who has to change in a school locker room should let the girls go free. She passed me notes in English class, crude stick-figure drawings of our teacher, who used too much self-tanner and smelled like cats. She linked arms with me as we walked down the hall, and every wildlife researcher will tell you that when it comes to survival in a hostile environment, a pack of two is infinitely safer than a pack of one.

One morning Chatham stopped coming to school. When I called her house no one answered. I biked over there to find a For Sale sign. I didn’t believe that she’d leave without any word, especially since she knew that was what had freaked me out so much about my mom’s disappearance, but it got harder and harder to defend her to myself as a week went by, and then two. When I started skipping homework assignments and failing tests, which wasn’t my style at all, I was summoned to the school counselor’s office. Ms. Sugarman was a thousand years old and had puppets in her office, so that kids who were too traumatized to say the word vagina could, I guess, put on a Punch and Judy show about where they’d been inappropriately touched. Anyway, I didn’t think Ms. Sugarman could guide me out of a paper bag, much less through a broken friendship. When she asked me what I thought had happened to Chatham, I said I assumed she had been raptured. That I was Left Behind.

Wouldn’t be the first time.

Ms. Sugarman didn’t call me back into her office again, and if I was considered the oddball in school before, I was completely off-the-charts weird now.

My grandmother was puzzled by Chatham’s vanishing act. “Without telling you?” she said at dinner. “That’s not how you treat a friend.” I didn’t know how to explain to her that the whole time Chatham was my partner in crime, I was anticipating this. When someone leaves you once, you expect it to happen again. Eventually you stop getting close enough to people to let them become important to you, because then you don’t notice when they drop out of your world. I know that sounds incredibly depressing for a thirteen-year-old, but it beats being forced to accept that the common denominator must be you.