Operation Bitemark is the military designation for call name Delta X-Ray delta, the mission is to get apparently ZN1-immune prisoner test subject Murphy to the CDC's research laboratory at Mount Wilson Station in California. The mission initially began with Lt. Mark Hammond evacuating Murphy from Portsmouth Naval Prison in an effort to begin the long journey to the west coast. Hammond and Murphy joined with the remnants of the Upstate New York survivor group to form the Westward-bound survivor group.
After Hammond succumbed to a zombie attack, Charles Garnett took over as leader of the group, and main protector of Murphy. Citizen Z, the sole remaining human presence at the NSA's Northern Light listening post, acts as the coordinating entity behind the mission after communication with military leadership is severed.