Robert Nightingale

In the game Alan Wake, the eponymous author finds himself pursued by rogue FBI Agent Robert Nightingale. As the plot goes on, Nightingale becomes intent on capturing Wake at all costs.

Alan Wake
Nightingale first appears in the game's Episode 3 "Ransom" answering a call from trailer park owner Randolph. Having investigated Alan Wake for a while, Nightingale relentlessly pursues the author through the trailer park, shooting at will regardless of the fact that he nearly injures Randolph in the process. Dismissing the trailer park owner, Nightingale fails to capture Wake and sends all local police forces in pursuit. At Pat Maine's radio station, Nightingale shoots at Wake several times, almost hitting Maine in the process but not caring a bit. He swears that he'll have Wake captured if it kills him. During many insults, Nightingale mockingly refers to Wake as several names of other authors.

Nightingale reappears in Episode 5, having arrested a drunken Wake and his literary agent Barry Wheeler while they were at the Anderson house, fighting off the Taken. He cruelly taunts Wake, declaring that the manuscript pages he found featuring Nightingale's name in the narration will put him away in jail for a long time. As an argument breaks out, Nightingale takes a glance at a manuscript page describing his capture by the Dark Presence. Sure enough, the shadowy monstrosity breaks into the police station and takes Nightingale away into the night.

Background
In The Alan Wake Files supplementary reading materials, Nightingale is given a far more sympathetic background explaining his actions than in the game. Prior to the story's events, Nightingale had a partner who was over time influenced by the Dark Presence and would avoid shadows at all cost until he was taken by the Presence. Determined to overcome his guilt over his partner's death and find the source of the affliction, Nightingale turned into the crude, demeaning, drunk, "cowboy cop" he appears as in the game. Influenced by nightmares featuring an individual similar to Alan Wake in appearance, Nightingale is led to assume that Wake is responsible and seeks to kill Wake if it would mean the end of the terrors of the Presence.

Aftermath
In the epilogue of the game that shows Bright Falls during the day and the surviving townsfolk, Nightingale is briefly seen in an aura of darkness. It is suggested that he may become the Dark Presence's new avatar after the destruction of the Barbara Jagger avatar by Alan Wake.