It was the briefest of glimpses, but he saw it. When the man raised his arm, his shirt sleeve lifted just enough for him to see the red splotches on his skin. Blood. Interesting.
The man was trying very hard to act casual. He glanced back down the hallway, and Sherlock took a second to catalogue as much about him as he could, storing it all in his mind for further use.
He laughed, grinning easily. "Oh, I'm the same," he said, jovially. "Don't know where I'm going half the time. And that's when I'm at home. I'm useless in this place."
"Actually, you wouldn't know how to get to the kitchen, would you?" he said, reaching behind him to scratch his neck nervously. "I've been wandering for ages."