Duncan is Dr. Busgang's Fulcrum handler, and part of the team developing the Fulcrum Intersect. He was responsible for Cole's capture at the end of "Chuck Versus the Beefcake" and attempted to extract Chuck's identity from Cole by means of torture. Duncan says that the members of Fulcrum are "patriots" who "do what needs to be done to preserve this nation's rightful place in the world." Duncan executed Busgang before being shot and killed in turn by Sarah.
According to NBC.com, Duncan was once a Marine Corps sniper who was honorably discharged after serving with distinction during Operation Desert Storm. He joined Fulcrum due to growing disillusionment after his discharge.