Simon didn't get the whole Dark thing and he was content to lose himself in the books on 'modern' medicine he found in the Medbay. He certainly understood why people were leaving. Someone who fed on negative emotions should be avoided by some of them at all costs. His first instinct was to grab River, listen to Kat's advice, and run like hell. But his sister was stronger than he admitted sometimes. And she was useful. Unless she specifically asked to leave, or at least implied it was what she'd rather do, he was going to stick this out. There was no way this Dark was going to play on him. He understood his faults better than most and had accepted his mistakes in life.
But he also wasn't dumb enough to put himself in the middle of all of the investigations either. So he was sitting at a desk in the office reading about 'modern' methods when he heard a soft sound. Glancing up, his eyes widened for a moment before he shut the book and looked up with a smirk.
"This doesn't look like China. Not that I know at all what China of this planet looks like. But I don't think this is it. What's wrong?"
Because it was obviously not just a social visit. Social visits didn't really happen with him. So clearly something had gone wrong in China and she needed a doctor. And just happened to get him. She'd have been content with anyone.