There was a long pause when Sherlock was silent. It was partially because for a few moments, he wasn't quite sure what exactly to say, but it was more so because he was taking all of the information in, parsing it out, making sense of it.

If that could even be done.

"I know." He said, before he could think about what he was saying. "Somehow, when I said the name, I knew that was you. And that makes no sense to me. How could I know? You are John Watson, formerly of the Fifth Northumberland Fuseliers. At least, that is what you told me. I;m not exactly sure if that is the truth or not any more, though you do certainly hold yourself in a military fashion."

Sherlock clearly by the way he was studying the man in front of him, the man he thought was John Watson, did not think he was crazy, or that he was lying. Not any more at least.

"If you are who you say you are... " He started, choosing his words carefully. "Then... why come to me? Why tell me that you are.. Merlin.. that you know magic, and that you are apparently millennia old, if not older? Why me, of all the seven billion people on earth?"

Sherlock had a feeling that there was more to this, though he wasn't thoroughly convinced that he wanted to know.