When a female cop is shot while responding to a call, her husband, an NYPD captain, blames her partner and wants to seek his own revenge. A new assistant district attorney, Valerie Heywood arrives to handle the case and prompts concerns with her by-the-book approach. Sorenson must make some important decisions in his personal life, which is bad news for Mary Franco and maybe good news for Diane.

Notes

• First appearance of Garcelle Beauvais as A.D.A Valerie Heywood
• Richard Brooks guest stars as Capt. Eric Knowlton
• Eugene Byrd guest stars as Andre Cutler

The detectives are suspicious of a Russian widow's alibi when her husband is found floating in the East River. Medavoy's newfound interest in the Chinese language comes in handy when he and Detective Harold Ng (Episodes 2.3 & 3.9) help an immigrant family rescue their kidnapped relative. Diane is emotionally conflicted about the end of her relationship with Danny.

• Tzi Ma guests as Det. Harold Ng

A trio of Goth teens are involved in a stabbing during a night of wild partying. New evidence gives Sipowicz the opportunity to save the case Sorenson mishandled. Russell works with Connie McDowell, who has to overcome brief hostility when she fills in for Danny. Andy delivers Danny a stern lecture about how his recent words and actions make him difficult to work with, affecting both the detective squad and the cases they are attempting to solve.

Note:

• First appearance of Charlotte Ross as Connie McDowell.
• Pedro Pascal guest stars as Shane "Dio" Morrissey.
• Taryn Manning guest stars as Tracy, a witness to a homicide.

Sipowicz and a fully reinstated Sorenson work to help an officer's relative whose temper gets him in trouble, while the rest of the detectives investigate an apparent stabbing attack on Captain Bass' wife. Romance blossoms as Sipowicz spends more time with Cynthia and Baldwin Jones has a date, while PAA John finds an admirer in an antiques store owner.

Note

• Scott Lawrence guest stars as Anthony Mackey

Sipowicz's split-second decision during a shooting puts his entire career in jeopardy unless a missing crime victim can be found to corroborate his story. Danny and Diane team up to find evidence that exonerates Andy. A rape at a bar leads to a disturbing discovery that lets Connie close the case, leading to permanent assignment to the 15th precinct.

• Timothy Omundson guest stars as Seth Werna, the department Shrink.
• Eric Balfour guest stars as Eli Beardsley.

Andy has an unusual response upon hearing the news that Fancy is leaving the 15th precinct. Russell and McDowell work to track down a severed penis in hopes of reattaching it to its owner. When Sipowicz and Sorenson investigate what seems to be a mob execution, their suspect makes a deal for immunity that leads to a suspect for a long-unsolved drug murder. Lieutenant Dalto takes over for Fancy and generates immediate animosity that makes the detective squad dysfunctional.

Notes

• Denise Crosby guest stars as Lt. Susan Dalto
• Ricardo Chavira guest stars as Customs Off. Kenny Sotomayor

As Fancy moves on to his new position as a captain, the sadness felt by the detectives of the 15th precinct is compounded by the chafing ways of Lieutenant Dalto. Fancy asks for a final favor from Captain Bass, resulting in Dalto's removal from command and assignment of a new lieutenant. A teenage immigrant girl with a troubled past is murdered and there are numerous suspects.

Notes

• Last appearance of James McDaniel as Arthur Fancy. Following this episode, Dennis Franz (who plays Andy Sipowicz) is the last remaining member of the original cast and the only actor to star in all twelve seasons and in every single episode.
• First appearance of Esai Morales as Tony Rodriguez.
• Denise Crosby guest stars as Lt. Susan Dalto

Sipowicz reaches out to an alcoholic ex-cop whose daughter has been murdered. The new squad commander, Lieutenant Rodriguez steps in when detectives from another squad try to take over the 15th precinct's investigation. Andy stumbles in his new relationship with Cynthia and turns to his ex-wife Katie for comfort.

Notes

• John Finn guest stars as Jimmy McElroy

Still grieving the loss of her husband and the failed relationship with Danny Sorenson, Diane leaves her job in order to get her life back together. Her unannounced and sudden departure causes hurt feelings, especially for Danny. Medavoy and Sipowicz go undercover to nab a pair of robbers who prey on the elderly. Andy wonders openly whether his plan to marry his ex-wife in order to create a stable home for Theo is a good idea. Danny meets a stripper while working a double-murder case and seems to be falling for her.

Notes:

• Final appearance of Kim Delaney as a regular cast member. Delaney would return as a guest star in five episodes during seasons 10 & 11.
• Final appearance of Debra Monk as Katie Sipowicz.
• Greg Grunberg guest stars as Joey Schulman

Much to Andy's displeasure, Danny seems to be losing himself in his relationship with Kristen, even placing himself in jeopardy in attempting to protect her from a rude strip club patron. Connie works with Greg on a case where a young woman manipulated two men into committing a robbery that turned into a double homicide. Katie and Andy make a crucial decision about their remarriage. Baldwin struggles to holds his temper in check while working on a case in which a woman was savagely beaten and her husband murdered for no apparent reason.

Note

• Greg Grunberg guest stars as Joey Schulman
• Last appearance of Rick Schroeder as Danny Sorenson, however he remains in the opening credits for the next episode.

Danny is missing, and his colleagues fear the worst. Kristen is found dead in his apartment. As the detectives desperately cling to the belief that Danny is not the murderer, concern and fear for his wellbeing cloud their search. Rodriguez gets the squad to focus on the job and helps them close a murder case involving a gay hustler and a minister's wife.

Notes:

• Greg Grunberg guest stars as Joey Schulman
• World Trade Center last appearance in this series