A hesitation, as Louis considers all the answer would encompass.

A passing thought: had Daniel omitted San Francisco from the book entirely?

"I knew him when he was a young man," Louis explains, slow over the words. "He was charming. I found him interesting, right away."

However—

"I think we should tell you the story of how we met together."

Or at least, Louis should impart it in person. With Daniel's permission.