- "Mrs Hudson's been attacked by an American. I'm restoring balance to the universe."
- ―Sherlock Holmes [src]
Neilson is a CIA field operative who interrogated Mrs Hudson. He was repeatedly thrown out a window by Sherlock Holmes in retaliation. He later meets Sherlock again and when the consulting detective asks how he is feeling, Neilson replies, "Like putting a bullet in your brain, Sir." and casually comments how he would get a medal if he did.