He looks at her, his expression serious, and nods.

"People said it was the government, and some people thought it was God or the dark man or some such thing. I don't really know what it was, except that everyone seemed to get sick of it. Far as I know, some idiot in a bunker broke a vial and then carried it on out to everyone else."

He pauses in his writing, and looks up at her with sympathy.

"I'm sorry. Didn't mean to upset you or anything--like I said, it's nice to know there's an earth where that doesn't happen."