One night in New York, a radio host named Erica Bain (Jodie Foster) and her fiancé David (Naveen Andrews) are walking their dog. Suddenly, they are attacked by three criminals. Erica is severely beaten but survives. David was not so lucky. His injuries were fatal. Erica is traumatized by the assault and unhappy with how the police are handling the situation, so she decides to take matters into her own hands. She gets an illegal weapon and starts wandering the streets late at night, searching for the thugs that did this to her. As she wanders, she finds she must use the gun to protect herself from other criminals. Detective Mercer (Terrence Howard) of the NYPD investigates the crimes she has committed without knowing that his friend was the perpetrator. Erica feels she must avenge David’s death by finding the three criminals, but the Detective is beginning to figure out her role in the crimes.