|Occupation||CIA Field Agent|
|Appearances||A Scandal in Belgravia|
|Portrayed by||Todd Boyce|
"Mrs. Hudson's been attacked by an American. I'm restoring balance to the universe."
Neilson is a CIA field operative who interrogates Mrs. Hudson. Thrown out a window by Sherlock Holmes repeatedly 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.