In the wake of the World Trade Center September 11 attacks and Danny's disappearance, the 15th Precinct faces a gruesome investigation when four young girls are found dead in an apartment.

Note When the undercover sting operation to flush out Danny's killer goes bad, there's a major gun battle in the streets of New York between police and a "made" man.

McDowell and Jones discover that a vintage '56 Les Paul guitar is a key piece of evidence in the death of a young, struggling musician.

Note A murder investigation leads Sipowicz and Clark to a deranged woman who is having an incestuous relationship with her teenaged son; Ortiz and McDowell investigate the death of a child killed by a stray bullet; Connie and Andy take Theo out to the movies; and, PAA John gets Andy's advice when considering a trip to Africa with his boyfriend.

Meanwhile, Sipowicz, who's avoiding McDowell after their recent kiss, investigates the murder of a rehabilitated felon whom he had long regarded as a foe; Baldwin is devastated by personal events but restores his friendship with Greg; Rita's husband swears he'll make her life miserable when she says her divorce decision is final; and PAA John's temporary replacement in the squad is not much liked by anyone.

An armored car guard is shot to death; a female bank employee is found dead in a dumpster; and Sipowicz intervenes in an attempt to save Lieutenant Rodriguez's job.

The armored car investigation reveals the culprit to be a bungling group of amateurs looking to pay off their bookie, and Andy confronts IAB Captain Fraker on the merits of his grudge against Rodriguez.

Meanwhile, a woman is busted for possession of narcotics that her son planted on her; one of three people shot execution-style survives; and, Medavoy's daughter threatens to elope because his ex can't face him at the wedding.

Sipowicz and Clark investigate the murder of a deli owner but begin to question the integrity of a robbery detective who is helping them with the case.