"Prince of the City" is a crime drama film released in 1981. It is directed by Sidney Lumet and based on the non-fiction book of the same name by Robert Daley. The movie stars Treat Williams as detective Daniel Ciello, who is a well-respected member of the narcotics division of the New York Police Department.
The story follows Ciello as he agrees to help the federal government in an investigation into corruption in the police department. The investigation was led by several federal prosecutors, including Rick Cappalino (Norman Parker) and Mario Vincente (Jerry Orbach).
Ciello, a corrupt cop himself, initially agrees to cooperate with the investigation in exchange for immunity for himself and his close associates, including his two partners, the trigger-happy detective Joey (Matthew Laurance) and the drug-addicted detective Shawn (Bob Balaban).
As Ciello provides more and more information to the Justice Department, he becomes increasingly implicated in the corruption and criminal activities of his colleagues. He starts to feel guilty for betraying his friends, and struggles to balance his loyalty to his fellow officers with his obligation to the law.
Ciello eventually learns about a scheme within the department to sell drugs to his street informants. In order to expose the conspiracy, he becomes an undercover informant himself and sets up a sting operation with the help of the FBI.
The film culminates in a powerful scene where Ciello testifies against his former colleagues in front of a grand jury, revealing the extent of the corruption in the NYPD. The movie ends with Ciello walking out of the courthouse alone, ostracized by his former friends and colleagues, and struggling to reconcile his own actions with his conscience.