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.

Donna's younger sister, Dana, arrives and moves in with her and Medavoy, and tries to make the moves onto him. Simone doubts the confession of his friend's 11-year-old son, a murder suspect in a gang related shooting at a school. Meanwhile, an HIV-infected Lothario comes to the station and asks Lesniak and Martinez for help when he appears to be targeted by a woman he's apparently infected.