“I did research, too,” I add, my voice soft.

Cora gives me another weighing glance. It reminds me of the way Mom looks at fruit at the grocery store, always searching for unbruised peaches and bananas that are at perfect ripeness.

“Yes, well, I did further research. Which brings us to step three, the hypothesis.”

I know I’ve barely spoken to Cora in almost a year, but if I know her at all, she already has a hypothesis.

“And I have a working hypothesis already.”

Yup. I was right. I smile wide.

“What?” Cora says, her eyebrows arching.

“Nothing—I just—I’m gl-glad we’re working on this together.”

Cora’s eyes narrow and her whole body stiffens. “I’m only doing this for Mabel.”

Cora’s words are like a hot slap across the face. I wince. “I know.”

“I debated a lot about whether talking to you again was a betrayal of Mabel.” Cora flips through her notebook and then holds it out so I can see the chart she made where she listed out the pros and cons of working with me.

“But I ultimately decided for a project this big, I need a partner. And you are the obvious choice. I’m doing all of this for my sister, though. It’s not about you.”

I bite down hard on my bottom lip. “I know. I want to help Mabel, too. And everyone else.”

I feel really guilty that, of the four people who died that day, I mostly think about Parker and Mabel. I wonder if that makes me a bad person. But I didn’t know Jessica Ogden or Mrs. Isabelle Martinez (who was a ninth-grade science teacher at Chestnut High School.)

I’ve practiced saying their names aloud in the dark. I whisper them to Cupcake. And I know what they looked like because I read all about them online, even though Mom told me I shouldn’t. Or rather, she banned me from looking them up. But I still did.

When I whisper their names, I visualize sending comfort to their families. I repeat the details I learned about them like how Jessica played the clarinet in the band and liked to volunteer at the animal shelter. And how Mrs. Martinez was the mom of a little boy and a talented long-distance runner, and enjoyed going bird-watching on weekends. I force myself to think about everything their families have lost because of Parker, but no matter how hard I try to concentrate, my mind always goes back to Mabel.

And to Parker.

That probably does make me a bad person. A familiar guilt swims around inside of me.

But if we fix this, if we really find that wormhole, maybe it will be okay that I didn’t spend enough time thinking about Jessica or Mrs. Martinez. Maybe I’ll be forgiven because I’ll be saving them, too.

“Have you thought about when we want to time-travel back to?” I ask. “Isn’t that the most important thing?”

Cora’s posture stiffens again. “Yes,” she says sharply. “Won’t we just go back to that morning? Isn’t that we’re trying to stop? Besides, that morning makes the most sense. Since we weren’t there when it happened, that means we won’t risk running into other versions of ourselves, which would just make everything more complicated. You never want to run into your past self because that could have major time and space implications. You don’t want to mess with the time continuum.” She makes an exploding gesture with her hands.