A group of detectives and officers work at the 15th Precinct, a seedy police station in Manhattan, New York City. Detective John Kelly, a 15-year veteran of the force, deals with his partner Andy Sipowitz, an alcoholic 20-year veteran detective. Laura Michaels, an aspiring lawyer and Detective Kelly's wife, is having problems with their marriage and she hires Josh Goldstein, a lawyer who lives in apartment 4B of their building to work on a divorce, who gets mugged in the laundry room of the building. Meanwhile, Sipowicz is relentlessly pursuing mobster Alfonse Giardella, who threatens Sipowicz to leave him alone. Later, Sipowicz is shot by Giardella during a tryst with a prostitute. Enraged, Kelly orders the precinct officers to hound Giardella and his ruthless employer; mafia kingpin Angelo Marino. The new patrol officer, Janice Licalsi, is attracted to Detective Kelly. But is she is revealed to be an informant for Marino who orders her to murder Kelly.

Inspector Lastarza of the Organized Crime Unit tells Lt. Fancy and Kelly that they stop applying pressure to the local mob for their pursuit of Angelo Marino is hurting the FBI investigation to nail Marino. Meanwhile, Sipowicz regains consciousness in the hospital after the shooting, but he has no memory about the attempt on his life because he was drunk at the time. Laura and John Kelly become officially separated and she decides to join a private law firm. Josh "4B" Goldstein becomes more paranoid about his mugging and brings a gun into the laundry room every night in hopes to catch his attacker. Kelly tries to reason with a deranged man who has taken a judge hostage who let his son's killer free. Elsewhere, Angelo Marino puts more pressure on Janice to murder Kelly, but she kills him and his chauffeur/bodyguard instead and slips away.

Janice's policeman father arrives for a visit and tells her about his pending indictment for corruption involving being an informant for Angelo Marino when a book that Marino had on him as a list of all of his informants... including hers. Sipowicz makes some appearances at the hotel where Giardella is staying to further intimidate him over the shooting death of Marino. Meanwhile, Kelly and Martinez are assigned a case involving the robbery and murder of a woman. Also, Josh Goldstein comes to the precinct in search for his gun he used to kill his assailant.

Kelly begins moonlighting as a security guard for Susan Wagner, a wealthy woman who's married to an abusive husband. But things take a turn when the husband is shot and killed, and Mrs. Wagner becomes a suspect. Meanwhile, Sipowicz is paired with the hard-nosed Detective Walker who arrests a man for a robbery and double-murder. While Detective Walker thinks he's guilty, Sipowicz thinks differently. Laura quits her job and plans to move into a position with the District Attorney's office, prosecuting narcotics. The increasingly edgy Josh Goldstein has Kelly appear at a tenant's readiness group regarding crime, and he is later killed trying to save an elderly woman from a mugging on a subway platform.