Paul came by on Sunday evening. I should have expected him. In all worlds we had tutoring on Sunday, although in the last couple it was as much chemistry as it was math, so to speak. But not anymore. Today, he was a bit formal, and all business. It was both charming and troubling. My head was too stuffed to cram anything else in, but spending time with him was the best remedy for my woes, even if everything we studied went in one ear and out the other. We sat at our dining room table, in front of big french doors that overlooked the pool. We had actual books instead of digital ones, because our math teacher believed algebra should always have weight.

“Okay, so this first problem isn’t all that hard,” Paul said. “Two cars are traveling south along a highway. The first is driving at fifty miles per hour, and the second, which leaves ninety minutes later, travels at sixty miles per hour. How long will it take for the second car to catch up with the first?”

“Are they in the same universe?” I asked.

He grinned. “I assume so.”

“What color are they?”

“It doesn’t matter.”

“It does if they’re not the same color that they started.”

He looked at me, trying to figure out why I was being so obtuse. Then he came around the table and sat next to me. Taking my pencil, he slowly wrote out the equation in front of me. “I think you’re letting yourself be distracted by details,” he said. “When you strip everything else away, it’s a simple equation.”

But my eyes weren’t on the numbers, they were on his hands. The way his fingers moved so confidently on the page. I could smell the shampoo he had used that morning. Coconut and cherry. I loved the smell of his hair. I had once told him that—but not in this reality. Here, I was nothing to him but money he was saving for college. I knew the schools he had his eyes on. I had my eyes on those schools too, even though I knew, short of a scholarship, my chances of getting into the same schools as Paul were slim. Was that in my original world? No, I don’t think so, but that didn’t matter to me anymore.

“See?” he said, solving the equation. “Numbers never lie.”

I felt my eyes begin to tear up. “They do sometimes.”

He didn’t know what to make of that. “Hey . . . are you okay?” He took a long look at me, and I couldn’t look away from those eyes. Two primordial black holes like portals to every place I wanted to be.

“Listen, if this isn’t a good time—”