He's doesn't know what to do with that—that straight-faced pronouncement from a girl in sodden clothes. His first impulse, and he loathes himself for it, is to turn it into a joke. (“Does everyone get one of those where you're from?”) William keeps his eyes on her, rather than the set of reflections smiling their tender smiles.

Why “was”? But he's not ready to ask.

“Before you got here”—he smiles her way, though she can't see it—“I was thinking about where they came from. I—” His voice snags and he loses it completely, takes a slow breath. “If it's like a prism—if it splits us into...” The people they're made up of.

He doesn't voice the alternative: that somewhere, sometime, Dolores and David look in a mirror, or a pool of clear water, or at the wall of this same cave, and see them looking back. “What did he sound like?”