Det. Casey Shraeger meets the other zany but secretive detectives which make up the homicide squad in which she was just transferred to. Her partner will be Det. Jason Welsh, who is already working on a case of who killed his former partner.

A family of criminals has the detectives running all over the city until Walsh and Shraeger discover their motives and negotiate a stop to all the crime. Brown has Shraeger investigate Walsh's past because her former partner turned out to be a dirty cop. Meanwhile, Cole's former partner in crime returns, making it even more difficult for Cole to continue to hide his criminal past.

Banks and Delahoy investigate a store selling murder weapons and instructions on how to get rid of the body. Nixon asks Casey to help get a client's son out of trouble on a bogus charge.

When Beaumont is in a pawn shop to get some cash the shop is robbed by a man and a woman. The woman is later the target of Shraeger and Walsh's investigation when she robs a bridal store with a different man.

Beaumont is struck when Lutz pulls a gun at Walsh's diner. While investigating, Walsh and Schraeger uncover Lutz and Cole's past connection. Elsewhere, Banks and Delahoy get help from a clairvoyant passenger when they investigate a rash of bus robberies.

Walsh and Shraeger try to help Powell, who fears he may have killed someone during an alcohol-induced blackout. Meanwhile, becoming victims of identity theft inspires Banks and Delahoy to make some changes in their lives.

Casey and Walsh are placed on protection detail of a wealthy businessman, George Reed, who had recent threats made on his life. Responding to screams they hear, they leave their post in front of Reed's hotel room and, when they return, find his room is trashed and him gone. Then a ransom call is made asking for $10 million for his safe return. Meanwhile, Banks and Delahoy are put on the case of an 87- year-old man on a geriatric crime spree.

Alvarez takes over while Sergeant Brown is away. Things go south when Alvarez releases Bo Keebler, a man who recently tried to rob a Chinese restaurant, into the custody of U.S. Marshall Foster. Casey Alvarez, and Walsh discover information that suggests Foster isn't exactly who he claims to be after the precinct receives a bomb threat. Banks tries to stay in his apartment until after his 43rd birthday to keep from being killed.

When a drug store owner is shot while running down the street naked, Walsh and Shraeger investigate. Information from the boyfriend of the victim's daughter leads the detectives to a loan shark that the victim had an argument with a few nights earlier. After a series of tapes from an apology line service turn up missing Beaumont and Cole look into the theft. Meanwhile Delahoy convinces the medical examiner to give him an MRI, and he receives some unexpected news.