In the series finale, a boxing promoter is killed, and three possible suspects emerge: his girlfriend; a damaged fighter that he didn't want in the ring; and his nephew (who was also his business partner). Meanwhile, Dunbar considers working without a gun.

Dunbar's gun is stolen and he suspects it may have been used in a murder, and a high school boy with connections to drug dealers is shot dead.

When an old woman is found dead in an arson-caused apartment fire, Dunbar and Bettancourt investigate. And the man who found Dunbar's missing guide dog, Hank, asks Dunbar a favor -- to counsel his nephew who is also losing his sight.

When Dunbar poses as a drug dealer to solve a murder, he is beaten up by thugs who also steal his seeing-eye dog.

Dunbar and Bettancourt investigate the murder of a man shot in the face, but the murder victim's identity cannot be confirmed. Meanwhile, Bettancourt won't forgive Dunbar for chasing off her boyfriend without first telling her of his criminal background.

Dunbar and Bettancourt force a mother to give her child to its father in a bitter custody dispute. Meanwhile Dunbar tells Bettancourt's new boyfriend to end the relationship or have his arrest record revealed to her, and an old Army buddy of Dunbar's confesses that he's responsible for the death of a platoon mate in Iraq.

Dunbar suspects murder when a man who was sexually molested in his teens falls to his death from a 12th-floor window. And Bettancourt unknowingly dates a nightclub owner with a criminal background.

Dunbar tries to redeem himself after he lets a man who murdered a Korean grocer escape, and the Chief of Detectives chastises Dunbar for pulling out his weapon in public.

Dunbar suspects a prison inmate when two women are raped and both have their faces slashed with a mysterious letter "Z".

Dunbar's former partner, Terry, responsible for Dunbar losing his sight, is shot with the same gun that killed two gang members.

When Detective Carl Desmond is found murdered, the squad thinks the killer is someone Desmond arrested, but Dunbar believes it's Carl's former police partner.

A 12-year-old boy is found murdered, and a known pedophile is the initial suspect. Meanwhile, when Dunbar goes into a jealous rage after sensing his wife's boss is flirting with her at a dinner party, she threatens to leave him.

The newest victim of a serial killer is found brutally murdered. Detective Karen Bettancourt, who had been working for eight months with Detectives Tom Selway and Marty Russo on the case, now finds herself re-assigned by the precinct's Lieutenant, Fisk, to partner with Dunbar on the investigation of a stolen car. Just as a resentful Bettancourt begins to think she's being completely marginalized in this new dynamic, Dunbar discovers that the stolen car may be connected with the string of murders.