"You'll be writing for a while." It's not a simple science by any means, so Tim settles for making it as simple as he can, by whittling it down to its most basic components: there's overlap. Some people remember. Some don't. There are apparently either infinite variations of the same person, or memories are more fluid in regard to being displaced from one world to another.

But then, mnemonic fluidity isn't a strange or new experience for him. That's not the part that's hard to believe.

"Memory," he says, tapping at his temple with the tip of one finger. "Boils down to memory. Who remembers who. Who doesn't remember what."