Dressed in a beige jumpsuit, with a GDI pass card and a black beret, Barker is just a simple soldier, working at the Supermax prison facility in the arctic circle.
After Cmdr. Parker is incarcerated for his participation in Louise James' coup and placed in a GDI Supermax Facility somewhere in the Arctic Circle, Barker is assigned to guard his cellblock. As the head of security for that sector, he is coerced by Agent Duquette into releasing Parker and letting him leave the prison undisturbed.
Barker appears in Tiberian Twilight.