Daniels was formerly involved in Treadstone, where he worked as a recruiter. He recruited Jason Bourne, then known as David Webb, in Operation Treadstone in 1997, and was present when Albert Hirsch was breaking down Webb in order to break his will to become an operative.
Sometime before or after Treadstone, he was reassigned as a station chief in Madrid, Spain, and at the time of Bourne Ultimatum acts as the primary source for Guardian journalist Simon Ross. Once he has been discovered to be the source of the leak to Ross regarding Operation Treadstone, he wires $100,000 dollars to a bank in Tangier, Morocco to which he flees and holds up in a hotel. He is later killed by an explosion set up by Desh Bouksani while in transit to the bank to withdraw his wired funds.
Daniels' first name is spelled both 'Neil' and 'Neal' in different places in the movie.