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.

Simone and Sipowicz help a local FBI agent, named Mike Frances, to investigate the murder of a local Italian mobster. However they are forced to commit robbery while working undercover for Agent Francis, and have to place a bug in the mob hangout. When two wise guys come to the station to file a robbery complaint, Russell and Medavoy catch them in the act of filing a false report. Meanwhile, Donna's hairdresser, Marina, tells her that she has a problem with her ex-boyfriend. He wants to hijack Marina's current boyfriend's truck, and Martinez goes undercover as Marina's boyfriend. But Lesniak is unable to hide her jealousy and possessiveness. Elsewhere, Andy Jr. learns more about being a beat cop with more pointers from his father Sipowicz Sr.