[Something stirs in the back of Sherlock's head, at this point. Some vague memory about bumping into a fellow wearing a blue suit, who'd seemed oddly familiar despite not being so physically familiar at all.]

Over a hundred years in the future, you say? That must make him a great, great grandson of sorts, then! Fascinating! To think, you would have descendants...! [That came out worse than it sounded in his head, though he doesn't quite realize it.]