“After I confirmed it, of course. It was fascinating to see her adjust on the spot. She said she’d wanted to believe it when you tried to tell them. That time travel was like you being gay—not something she could accept until she had a face to put on it. Once she decided to go with it, she was all in.” (Wait—did I inherit this trait from Mom?) “But really, Luis … she should be telling you all this, not me.”

As usual, Ms. Silverthorn is right. I do want to hear it from Mom. But that doesn’t mean I’m done with questions. “Mr. Gale is married to Chaz, and my mom believes in time travel … so the butterfly effect is real. Everything is different.”

“Everything? From what you’ve told me, that doesn’t seem true.”

She’s right. The school is here, and Cheng is here, and I recognize my classmates. “I don’t get it.”

“I only know the current timeline, so I can’t compare in any depth, but you’re still my student, and the school is still here. However, I do have a thought.” From her desk drawer, she produces a stack of books on time travel. From mid-pile, she retrieves a slim volume titled Limited Ripple Theory. “I try to keep up with all the latest, but perhaps I can stop now—you’ve proved one theory true.” Silverthorn taps the author photo, a black-and-white shot of a commanding-looking Indian woman. “She’s an astrophysicist who argued that time travelers only influence the trajectories of individuals upon whom they have made enough impact. And of course, the lives they change make their own impacts, and so forth. But they won’t change everything—no more than a freak storm in Antic Springs can affect all eight billion people on earth. Ripples are real, yes, but they eventually smooth out.”

“And everybody in this version of our time knows about this?”

She chuckles. “No, not at all. People think this woman has gone off the deep end. As they will also think of you if you run around telling your story. Your mom and I have been waiting for this moment so we could both warn you off. You can be out about anything you like except this.”

I don’t care what others do or don’t believe anymore. “Sis,” I say, “you know me. I am never shutting up again!”

Nix drives me home. All the way, I keep staring at them to make sure they’re the same. Despite my boast to Ms. Silverthorn, I’m suddenly nervous about spilling the beans. I’m also wondering how much of my high school experience did or didn’t happen. Oh my god, will I have new memories in this timeline and lose the old or keep both sets, and how will I tell the difference?