The movie opens with a confession. Staring straight into a video camera, "Turk" (Robert De Niro), a 30-plus-year veteran of the NYPD, recounts eleven cold-blooded killings, none of which were committed in the line of duty. Instead, they were the work of an unbalanced rogue cop who, unbeknownst to everyone around him, has become a lethal vigilante, a "street sweeper" ridding the city of rapists, murderers, thugs and pedophiles the justice system has failed to keep off the streets. A flashback reveals the moment that triggered this spree of "righteous kills." Four years earlier, Turk and his partner (Al Pacino), a detective who also goes by his precinct nickname, "Rooster", watch helplessly as Charles Randall (Frank John Hughes), a man who they both know raped and killed his girlfriend's (Melissa Leo) 10-year-old daughter, is acquitted by a jury of his peers. Outraged at the injustice of it all, Turk decides to cross the line and plant a gun in Randall's apartment, thereby setting him up to take the fall for a crime he didn't actually commit. Rooster, who clearly loves and respects his partner, has his reservations but goes along with it. Not long after, a brutal, smalltime pimp is found shot in a back alley, followed soon after by a pedophile priest and a rapist who got off on a technicality. In each instance, a short poem recounting the victims' sins is found at the crime scene, leading Lieutenant Hingis (Brian Dennehy) to believe he has serial murderer on his hands. Unaware that the killer is one of his own, Hingis pressures Turk and Rooster to find the killer fast, and they're soon joined in their investigation by Detectives Perez (John Leguizamo) and Riley (Donnie Wahlberg) who've been working a similar killing. Perez, however, senses there's something not quite right about Turk, and soon realizes that all the victims are somehow connected to this veteran cop. Turk's girlfriend, Detective Karen Corelli (Carla Gugino), a detective on the NYPD crime scene unit with a taste for rough sex, also begins to suspect that the killer might be someone within the department, especially after she makes a connection between the gun found in Randall's home and the guns the so-called "Poetry Killer" has been leaving behind.
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