FBI agent Robert Nightingale went to Bright Falls searching for Alan Wake with the intent of arresting him. He learned about Alice Wake's disappearance and believes Alan is somehow responsible, though his perceptions could be influenced by his knowledge of the manuscripts and their power over live events.
His dogged determination and personal journal, found by Clay Steward, suggest that Nightingale may have personal reasons in pursuing Alan.
Interviews with citizens of Bright Falls reveal that Nightingale is a loose cannon and possible alcoholic. When confronting Dr. Emil Hartman, the agent is both drunk and belligerent, his anger compounded by a sense of failure.