When NYPD Auxiliary Police Officer Heather Peterson is murdered, the detectives find her diary that details the sexual habits of the police officers at the 15th precinct. These findings cause the detectives to suspect the officers of the 15th precinct had something to do with her death, and the investigation of the cops cause tension between the officers and the detectives.
IAB start interviewing the officers who were in the diary, and Sipowicz and Clark are blamed as rats. A social worker appears to have taken her own life. A former cop wants his ashes buried at the precinct.
Andy and Theo move out. Tony thinks about calling it a day with his ex-wife. Sipowicz and Clark Jr look into the threats made to Clark Sr. A distressed, schizophrenic young man keeps saying "she can't breathe".
Clark is placed under arrest after police find heroin in his car; detectives search for clues when a woman is beaten to death with a cordless drill; a murder victim's obsession with clean living may have led to his demise.
In hopes of freeing Clark from jail, Sipowicz searches for drug dealers who might have a connection to Laughlin; McDowell and Ortiz investigate a series of rapes in a park involving a perpetrator who forced his victims' boyfriends to watch.
Sipowicz and Clark investigate when Julian Pisano is wounded in a shooting incident; McDowell and Ortiz assist a woman who doggedly pursues justice when she's conned out of $100; Clark grows concerned when his father stops returning his phone calls.
The detectives investigate the murder of a gay financier whose death might be tied to a marine; Medavoy and Jones search for answers when a strangler attacks a Russian mail order bride; Haywood feels threatened when a murderer's conviction is overturned.
As Andy and Connie prepare to finalize the adoption of baby Michelle, Frank Colahan's mom and dad show up. Connie sweetly and sincerely tells them they want the grandparents to be part of Michelle's life to the fullest extent possible.
A meek and mousy young woman is found beaten to death on the floor of her apartment. Her brother-in-law is very upset but not about her death--he was paying her money to use her apartment for an extramarital affair.