New York City detective Al Russo is a walking cliché and he knows it. His obsession with his job and the adrenaline rush it brings has led to a failed marriage and a taste for alcohol.
Detective Russo is called to investigate, what appears to be, a simple traffic accident that resulted in the death of a homeless person. However Al uncovers evidence that things may not be as they seem. His suspicions appear to be confirmed when he is confronted one night by a shadowy figure claiming the accident was actually murder. The figure threatens violence unless the perpetrators are delivered to him to extract vengeance.
The threats are followed by several unspeakable acts of savagery that are meant to send a message. A police operation hastily organized and executed to apprehend the person responsible for the violence ends in bloodshed and death.
Detective Russo now finds himself alone tracking an ancient enemy of man long since dismissed as legend. He must put his own life in danger and betray everything he believes in an attempt to prevent further bloodshed that would result in the deaths of tens of thousands.