Just days after Sylvia gives birth to a baby boy (Theo), Sipowicz suffers an emotional setback when Andy Jr. is found murdered in the line of duty. Sipowicz wants Simone to lead the case of his son's killer and also wants the opportunity for restitution. With Russell in tow, Simone tries to balance his desire for revenge, as well as his quest for justice to catch the killers. While Sipowicz breaks the news of his son's death to his first wife, Katie, he begins to show signs of an emotional breakdown. In the midst of all this turmoil, Donna makes her decision when she quits her job as administrative assistant to the precinct and moves to California, leaving New York for good.

Sipowicz helps his ex-wife deal with a drunk-driving violation. Simone's body rapidly succumbs to infection in the wake of his heart transplant.

Dornan causes problems at an AA meeting and Andy asks the Lieutenant to talk to him. Dolores' father accuses the squad of withholding information from him about his daughter's murder. Jill splits from Cohen.

Andy and Theo struggle to live without Sylvia, and the squad worries about them. Cullinan is confronted with new information about Mike's death. John is released from hospital.

Andy is finding Theo a challenge. A man is found dead in a hotel bath-tub, minus a part of his anatomy and some personal effects. A mother brings her son into the house because she thinks he's been stealing.

A young boy is suspected of killing his mother's boyfriend; Fancy realizes that Lt. Abner is severely depressed. Sipowicz has a date with a niece of a friend as a favor; Katie becomes upset at this news.

Jones uses his charm to help Andy and Danny solve the murder of an elderly couple; Medavoy gets involved with an old friend who is having trouble with the Chinese mafia.

Andy goes into a tailspin when a doctor's visit reveals that Theo may have cancer. Diane and Jill's relationship suffers when info about Jill's ex-husband surfaces. Andy and Danny ponder the impact on Jill's career.

IAB is closing in on Jill. Jill explains the leverage Don has over her. Andy stays by Theo's side as he undergoes tests to determine if he has cancer. Changes are made in the department as fallout over Jill's ex-husband.

The detectives investigate a multiple homicide at a fast food restaurant; an addict gives his 5 & a half year-old daughter to a drug dealer as collateral on an overdue loan; Internal Affairs reopens the Kirkendall case.

Danny wakes up in Diane's bed. Andy and Katie get Theo's test results. A former colleague of Bobby's reaches out to Diane from prison. The team investigate a series of cab-driver shootings.

A female officer is shot following a stationery store robbery and later dies in hospital. Danny tries to keep Diane safe. A new ADA arrives. Katie decides to move back home.

Rodriguez mediates when Sipowicz and Sorenson clash with detectives from another squad anxious to solve a multiple murder case; Medavoy and Jones try their hand at making extra cash by cleaning up murder scenes.

Sipowicz and Sorenson investigate a case involving an off-duty police officer who was shot in the company of a prostitute; Medavoy and Jones aid a hapless bodega owner by concocting a story to keep him out of jail.

Jones and Medavoy investigate the murder of a Chinese restaurant owner. An IRS lawyer claims to have been kidnapped and released, but Sipowicz and Sorenson doubt his story.

Sipowicz and Sorenson investigate the murder of an exotic dancer; Sipowicz and Medavoy act as elderly decoys to catch some street thieves attacking old people outside a local bank.

Sipowicz and Sorenson investigate the murder of a drug dealer, while Sorenson continues to see the stripper, Kristen, who draws him into a favor for the owners of the Tailfeathers club.