Donnie was pissed when I got to the lab. “Dude, I don’t know what’s going on with you. First you complain about not having enough time in the parallel dimension, now you’re showing up late? I need you here, we’re totally falling behind on the mouse experiments.” It was true. For all practical purposes, I’d been gone from the lab for weeks; progress on the next stage was slowing.

“Don’t we need more data?” I asked.

“I’ve got tons of data. Seriously, you’ve got to stop messing around with your second girlfriend and get back to work.”

“Oh, man,” I said. “That’s really going to mess things up for us.” I sat there wondering if there was a reality where both Erins would fall in love and we could have a deeply meaningful threesome. I asked Donnie what he thought. “It’d be amazing, right? Though, I guess it might feel kind of narcissistic. Still, if you didn’t want to hook up with yourself, does that mean you secretly have low self-esteem? What do you think? Would you ever make out with yourself?”

“Luke, what the fuck’s wrong with you? I need you here in the lab with me to write new programs. We’ve got a serious situation on our hands. Have you even been reading the notes I left you about wave temporality and the dangers of collapsing timelines?”

“Um—”

“Okay, we’re cutting you back to three hours.”

Donnie was, of course, right, but mostly I was thinking about how hard it’d be not to see the other Erin. Plus, I knew I had to tell her about sleeping with this-reality Erin, but Erin just jumped on me when I appeared at the lake house, and we stripped each other naked and made love instead.

It was deep winter, the light already gone, and we lay in her bed, the candles flickering against the walls, watching the sun disappear behind the pines at the far end of the lake. Her hand was against my chest, her touch reminding me of all the mornings we’d woken up in bed together in our other reality, back when we’d find each other beneath the blankets, feeling as though we were the luckiest people alive.

“I’ve been feeling strange,” Erin told me, her face highlighted by the glow of the candle. “It’s like I’m living these two different lives that can never match up. I can’t text, can’t call, can only wait around for you to show up, and then you have to leave whenever your lab buddy calls you back. And meanwhile, the real you—the one in this reality—is just some married beefcake dude. What’s that even mean? Is that secretly the real you?”

“No. This is the real me.”