After spending the first four periods scouring Dopney’s social media sites, Adam finds a picture of Dopney’s feet hovering over a bird’s-eye view from the Skydeck’s glass balcony 103 floors above Wacker Drive. Makes me nauseous just looking at it. No caption, no mention of anyone else he was traveling with or visiting. Just the picture that, luckily, Adam recognized.

“Two trips in three years? He must have been visiting someone,” I say with more conviction than I feel. The truth is, I need Dopney to have a connection so badly I’m almost willing to invent one for him.

I prop my foot on a stepstool Adam stole from the biography section and shift in the boxy wooden chair. It has to be the most uncomfortable chair ever created, like the school needed another way to torture its students. On a desktop tucked into the back corner, I scroll through old yearbooks uploaded in our library’s database, looking for Cropped Hair Girl while Adam sits beside me manning his iPad. At his insistence, both of us are signed in to his school account, not mine.

I point to a strip of electrical tape over the camera on his iPad. “What’s with that?”

“Precautionary measures. These things are incredibly easy to hack. This”—he flicks the tape with his finger and raises his eyebrows like I should be impressed—“prevents anyone from picking up the feed.”

Adam’s cell phone buzzes. He checks it before flipping it around to show me the latest picture Katie sent of a girl with short black hair. This one has a nose piercing, heavy purple eye shadow. I shake my head. To Katie’s credit, she’s had five passing periods and already sent half a dozen pictures of girls who fit the description. Unfortunately, none of them have been close. Same with my yearbook search, though I’m not sure I’d recognize Cropped Hair Girl with a different haircut. More than once, I’ve wondered whether I hallucinated this morning, made associations that don’t exist.

I think about what Cullen said about me—that I used to pretend my twin sister was still alive. He was right. I remember creating elaborate scenes involving the two of us having tea parties in the basement and dance competitions around our swing set. I remember talking to her about the routines we performed. I pictured her facial expressions when I dictated instructions, basically making her my backup dancer. She would nod like it was a good idea. I guess that’s the thing with an imaginary dead sister: she’ll do whatever you want her to do.